The long fix is -
1) Make sure your OS is set to show "Hidden and System" files.
2)Look for the BOOT.INI file in C:\,
3) Once you've found it, check the 'Properties' settings of its attributes and make sure it's not set to 'Read-only' (so you can edit it),
4) Open the file in Notepad, and delete any lines that refer to the 2000 you removed from the system,then save it.
5) Do a quick check of the file's attributes to make sure they're still 'Hidden, System' (the 'Read-only' attribute is not required).
The quick fix is -
Go to Start/Run/type :msconfig /Boot.ini tab -
then set the default OS to XP,and set the timeout to 0