A Default Gateway in most cases is a router, which possibly knows where to route every packet, if it doesn't know where, it will drop the packet.

--->A situation where you might knowingly/unknowingly configure two default gateways:


Using a desktop PC with two NICs or a laptop with a Wireless NIC and a LAN, you try to configure a brand new network device or change already configured network device like a Access point, Switch, Router, Wireless Bridge etc at your work place or at home. You would be on your corp-network/Internet through your primary card i.e. say NIC1. You will connect the device to your laptop/PC using a cross-over cable if a router or a Straight-through cable if a switch to your second NIC, and then you put in IP, Netmask, Gateway info on this card, say NIC2. With this setup you will have network connectivity issues. This is due to fact that, your PC/laptop's routing table has two default routes with two different EXIT INTERFACES causing confusion as to which one to use to send packets. Below is routing table of one such example from a Windows PC.
Here Corp-network is 10.10.100.0 and the Network device is on 192.168.2.0 Subnet.

IPv4 Route Table
===========================================================
Active Routes:
Network Destination               Netmask          Gateway       Interface          Metric
          0.0.0.0                            0.0.0.0      192.168.2.1    192.168.2.104     30
          0.0.0.0                            0.0.0.0      10.10.100.1        10.10.100.5     30
        127.0.0.0                      255.0.0.0          On-link                127.0.0.1    306
        127.0.0.1           255.255.255.255         On-link                127.0.0.1    306
  127.255.255.255     255.255.255.255         On-link                127.0.0.1    306
      192.168.2.0             255.255.255.0         On-link        192.168.2.104    286
    192.168.2.104       255.255.255.255         On-link        192.168.2.104    286
    192.168.2.255       255.255.255.255         On-link        192.168.2.104    286
        224.0.0.0                       240.0.0.0         On-link                127.0.0.1    306
        224.0.0.0                       240.0.0.0         On-link        192.168.2.104    286
  255.255.255.255     255.255.255.255         On-link                127.0.0.1    306
  255.255.255.255     255.255.255.255         On-link        192.168.2.104    286
===========================================================

From the above table we can see that there are two default route entries and so the PC would be confused which interface to use as its exit interface.

Solution:
Solution to this is to leave out the Default Gateway entry blank on the NICs of the PC, like in this example: -------------------------->

With this setup you wouldn't have any network issues reaching your corp-net/internet. Per the example in picture PC now has only one route entry for 192.168.2.0 Sub-net whereas it had two entries before, one for 0.0.0.0 i.e. "any" and another for "192.168.2.0", Notice this as highlighted in the route table above. Now the your PC knows to only send packets destined for 192.168.2.0 Sub-net on NIC2.


If you want to be more granular and tell your PC exactly which NIC to use when sending packets with certain destination subnet, you can do so by manually adding a route entry like below.

C:> ROUTE ADD 192.168.X.0 MASK 255.255.255.0 192.168.X.1

Description: route ADD “network” MASK “subnet mask”  “gateway ip”
What this is saying is anything with destination IP in 192.168.X.0 subnet send it to gateway 192.168.X.1
 
With this setup you should have no issues reaching your Corp-Network/Internet as well as the 192.168.2.0 network simultaneously.

• Click the windows start button or open the Run window and type - taskschd.msc and hit enter OR type "task scheduler" in search field of the windows start button and open it.
• Expand - Task Scheduler Library, Microsft, Windows and you'll see - Time Synchronization, almost at the bottom.
• Click that and all you need to do to set the time synchronisation at windows startup is self explanatory from the figure below (In step 2 Rt click and select properties).

After replacing windows vista with windows 7 ultimate, things worked pretty fast like in XP but with features of vista. First thing to do after installing, however, is to install the drivers. On HP support I saw that there are no drivers under windows 7 32 bit OS, but the drivers under Windows vista section worked great. Everything went smooth except that in Device manager there are two "Base system device" with unknown device symbol. Here's what I did to get rid of that after searching online in google.

I found that it was the card reader which had no drivers to support, so I went here
http://www-307.ibm.com/pc/support/site.wss/document.do?lndocid=MIGR-69983
and downloaded the files and then installed it and Voila! It worked.

If you upgraded from vista to 7 on dv2700 you might as well be missing the same drivers. However, its good to find out what exact drivers are needed for your particular hardware.

How to find and install drivers for your computer's hardware:

• Right click your My Computer and click properties , in the window click "device manager" from the left column.
• Right click on the device for which you're trying to find the drivers for and then click properties. 
• From the properties window, click on Details and from the Property drop down list choose "Hardware Ids."  In the Value section i.e. in the white area take note of the 4 numbers right after VEN or DEV as highlighted in the figure:
• From the figure vendor or VEN would be 8086 OR DEV or device would be 4229.
• With that info go to http://www.pcidatabase.com/ and enter either your VEN or DEV value and it will bring up very interesting information about your hardware. You may find direct address for drivers of your particular h/w or you can search google now that you know whats your hardware.

Thats all.

This post is about how I installed windows 7 and Fedora 12 on my HP laptop / notebook DV2500 / DV2700 and how I partitioned the disk.
Most of you already have some version of windows pre-installed and windows 7 doesn't need any guide on how-to-install. Its that easy. Anyway, this are the partitions I made on my 160GB hard drive.

Windows 7 (C drive)- 30GB primary
System Reserved - 100MB primary (i didn't create this one, windows 7 did that )
Fedora 12 - 13GB extended
Data - The rest of the Hard drive (yes, /boot for fedora 12 is on extended partition)

After installing Windows 7, hardware drivers, essential software like antivirus, adobe acrobat etc I am left with approximately 15GB of the C drive. Thats pretty cool compared to vista which took around 45GB but it included all the pre-installed HP stuff. I am sure 30GB is going to be quite sufficient for windows 7. With windows 7 laptop stays cool and the fan is on most of the time but very very low and it doesn't bother. So, for HP laptops known for heating issues, this is definitely a very good improvement.

From with in windows I created the 'data' partition leaving about 13GB for fedora.

Fedora 12 and its partitions:

• Download the Fedora 12 DVD ISO image from HERE 
• Fedora's Live-USB-Creator from HERE and install it. 
• Plug in your 4GB USB drive and open the live usb creator, you can see 'use existing live CD', click browse and point to where the ISO image file is and then click 'create live USB'. It takes some time.
• Once that is completed, your USB is NOT yet ready! with this USB when we reboot our system we can go up to partitions and then it throws an error. This just did not work for me.
• So, open the USB drive and from the folder 'packages' delete everything, this folder contains all rpms.
• Now, copy your Fedora-12-i386-DVD.ISO image file into your USB drive, not into any folders with in the usb drive but directly under the drive.
• You now may reboot your machine with your usb still plugged and it will take you to fedora installation.
• Just follow the onscreen wizard until partition, choose 'custom layout'

Partitions in Fedora 12:

• After selecting custom layout you'll see two hard disk's: /dev/sda - system harddrive and /dev/sdb - usb drive.
• /dev/sda already has three primary paritions -
• /dev/sda1 30GB,
• /dev/sda2 100MB,
• /dev/sda3 109GB(data).
• We now need to create the 4th partition /dev/sda4 and this is going to be our extended partition by default from fedora installation wizard. And we'll slice /dev/sda4 according to our preferences.
• /boot is a required partition, so select /dev/sda and click 'new', mount this on /boot, give a 200MB for size. This is our /dev/sda5 within our /dev/sda4 extended partition.
• Now, with in our /dev/sda4 we still have unallocated space which we can slice. I'd suggest like this:
•  Swap partition - 1GB atleast
• /home - 3GB or 2.5 GB and the rest to /

With the above settings we have these partitions in summary:
/dev/sda1 - 30GB windows C drive
/dev/sda2 - 100MB system drive
/dev/sda3 - 109GB and
/dev/sda4 - 13GB, this is further divided into
                  /dev/sda5 - 100MB for /boot
                 /dev/sda6 - 1GB for swap
                 /dev/sda7 - 3GB for /home
                /dev/sda8 -  Rest of the drive for /

After the partitions make sure to choose to install the bootloader to /dev/sda, by default it'll be /dev/sdb. Do not forget to change that.
And then continue with the rest of the installation.

Fedora 11 was very bad on my HP DV2500 laptop, heat was way too much. After googling and going through forums I came to know that the culprit was firefox, for some reason. Then I tried opera in fedora 11 and the heat was definitely very low.
Well, Fedora 12 improved on that, laptop stays absolutely cool. Like in windows 7, fan stays on most of the time but it does't bother and is very very low. And its the same when I used firefox but I got used opera and its a pretty good browser.