Hopefully not. When attempting your repair did you run the System File Checker?
Go to Start->Run and type sfc /scannow
You could also try getting a new rundll32.exe:
Put the Windows XP CD ROM disk in the CD ROM drive then go to Start->Run and type
expand D:\i386\rundll32.ex_ c:\windows\rundll32.exe
(assuming D is your CD ROM Drive)
Hope this helps