operating system help

I installed windows 2003 server on one partition. after the trial version was over I formatted the partition from the XP side .
How can I upload windows 2000 server on the partition that used to have 2003 server .
while starting the computer it still gives me 2 option of operating system i.e XP and 2003 server .If i select 2003 server it says that i dont have the boot files for that operating system .
How can i make use of that 45GB partition without affecting my other partition that has XP

Here is one idea re: 2000 & XP:

http://www.dougknox.com/xp/tips/xp_repair_2k.htm

Here is a more general search:

http://groups.google.com/group/micro...+server&qt_g=1