So many times I get the question about putting a large disk in a windows box that is not seen as the proper size. Whether it is windows 2000 or XP we can point you to the proper page at MS but after that you are on your own. If you are terrified by regkey edits call someone who can do this for you.
XP http://support.microsoft.com/default.aspx?scid=kb;en-us;303013
Win 2000 http://support.microsoft.com/default.aspx?scid=kb;en-us;305098