1 Put in your windows install cd and and boot it like you would if you were going to reinstall windows.
2 when the menu comes up select "R" for recovery console.
3 it should display something like this:
4 press the one key and then ENTER to select this windows install
5 It puts you in what is called a dos prompt
6 type FIXBOOT and ENTER, it will ask you to confirm (y/n) type Y
7 type FIXMBR and ENTER, it will ask you to confirm (y/n) type Y
8 type EXIT and Enter
after that it should reboot, hope this helps