There is also a great tool that I have used called emergency boot cd. It is found here: http://www.t4k.org/~ebcd/
It is an ISO image that you use to create a bootable CD containing a variety of tools. One on the tools is a master boot record tool which replaces grub or lilo in the MBR with the windows boot loader. I use this emergency boot CD because I no longer have a PC with a floppy drive.