Dude, formatting your HD is rather extreme for a GRUB failure. For future reference, all you need is a livecd (which you already have) and you also gotta know which partition you installed linux on. Assuming you reinstalled Windows, you can insert the Windows CDROM before your comp reaches GRUB, and from Windows Recovery Console, type "fdisk /mbr".
If that doesn't fix it, write back and I'll guide ya through a more complete recovery.
P.S: GIYF (Google Is Your Friend) and so is the search function at the top of this page.
