There are several grub repair utilities like
http://www.supergrubdisk.org/which allow you to boot from their CD and
recover the grub. If you need to
just restore the Windows boot process get a copy of the old DOS fdisk and
run "fdisk /mbr". This will rebuild the master boot record and remove
anything other than Windows boot information. I realize this information is
years out of date but it probably still works.