Where does computer stores the Operating System info

"There's the master boot record (MBR) and then there are various possibilities, depending on the boot manager your's using (Windows Boot Loader, GRUB/LILO or some 3rd party product).

If you restore the C: drive from a drive image, the original boot loader will be restored and the other operating systems will be still bootable.

Edit: you can use EasyBCD to edit the Vista Bootloader and fix problems."

"The information about partitions in stored in the 'partiton table' which is not really part of any OS.

It's information which describes the disk itself, not the operating systems you might have installed.

When the computer boots (probably from a bootloader) it goes to whichever partition you select and finds the information there, to boot the OS on that partition.

It's unlikely that a Windows virus would have touched the other partitions, but you'll have to try it out."