Restore your linux

Well.. let's go format Windows... thanks to the nice virus, but this will erase my ubuntu from MBR and I'll not be able to boot into it..
So, after installing windows and wiping out the windows partition. You get the ubuntu live CD and do the following:
sudo grub
find /boot/grub/stage1
This will tell you where are the boot files, something like hd0 or sda1, so you use that in the next step
root (hda0, 1)
setup (hda0)
quit
Remove the liveCD && restart your machine

Now you have a fully functioning Linux partition, if you haven't wiped it out accidentally while reinstalling windows.

More stuff in here:
http://ubuntuforums.org/showthread.php?t=224351