Yes, Windows seeks out and destroys any other bootloader when you try to install it. The easiest way to restore grub is to burn a copy (as an image) of Super Grub Disk and run it. It has an auto fix feature. http://prdownload.berlios.de/supergr...isk_0.9799.iso
If you have the ability to deal with bz2 files, then use this one: http://prdownload.berlios.de/supergr...0.9799.iso.bz2
- Bunzip it and then burn it as an image.
As to trying to dual boot Windows on your PC, did you tell the Windows installer to go ahead and reformat that partition? Now's the time to mess with it if you want, because if you try again in the future, it's going to zap your grub yet again. It's almost always best to get Windows running, before installing Linux. But, you can usually get it running and then use SGD to fix up grub if you've already got Linux installed.