But it is good that your drive with the other OS should be disconnected. And
when you reinstall Windows, your drive with the Linux OS should be disconnected,
so as not to damage GRUB. By the way, reinstalling Windows 2000 does not wipe
out GRUB, reinstalling XP does wipe it. Another issue: there are several types
of BIOSes, for the boot menu to appear there are specific keys, according to the
computer type: These can be F2, F8 (in my case), F10, F11, F12. There are some
that do not have a boot menu, at starting the PC you have to hit the Del key for
several times, enter the BIOS and set boot priorities from there.