open boot.ini with notepad
save as boot.old
delete the line
multi(0)disk(0)rdisk(0)partition(2)\WINDOWS="Microsoft Windows XP Professional" /noexecute=optin /fastdetect
and save as boot.ini
reboot the machine and check it boots to the correct version of windows.
if not then delete boot.ini and open boot.old
delete the other line. and save as boot.ini and retry.