I have a Win2k/Ubuntu dual boot situation. I have them on the same drive. I know that is hardly ideal, but necessary for the moment. Win2k is the first partition on the drive and I have my Ubuntu partitions after. Now my Win2k installation has become slightly corrupt, and I have not been able to repair it properly. I'd like to do a fresh new install of the Win2k, but that will wipe out the boot loader in the MBR. The question is how do I reinstall the boot loader after it has been wiped out? I've tried doing it through the install disk, but that made the whole system unbootable, and everything had to be completely reinstalled again, Linux and Win2k.

Check the Ubuntu wiki - pretty standard need. Don't understand why you would have had problems.
I typically just do it from something like Knoppix using grub commands rather than an installer. Either should (normally) work.

I assume you mean that your dual boot loader is now grub, and not win2k any longer. So, you are concerned that win2k will overwrite the mbr on your new install. I know a bit about how win2k does things, but not grub. However....

Here's a link that explains a lot:

http://en.wikipedia.org/wiki/Master_boot_record

Note there's a discussion on backing up your mbr using dd from linux.

I personally like system rescue but you can use any linux to rescue grub. After Windows destroys the mrb you need to insert you linux disc and boot into rescue mode. Once you get the command line, as root. Type:
Then you need to tell it what your root partition is. This depends on your setup. It might be (hd0,1). That would be the second partition on your first hard drive. If that is the right partition type:
then:
After that you can put grub on your mrb with:
You may need to change some things for your system.