this is a trick to get the command prompt back on a system where it is disabled and you don't have admin rights...

go to c:\winnt\system32\
copy cmd.exe to another folder (like desktop) and open it with a hexeditor...
now scroll down until you see the words "D.i.s.a.b.l.e.C.M.D." right after it there is a string which points to a place in the registry... just alter this string to something that doesn't excist (like microZoft, or polizies) and save the file.

now you can run the cmd from that location again...

this also works for regedit and taskmgr...

dunno if this works for XP too, but it's worth giving it a try