In this video, learn how to restore rundll32.exe on your Windows XP machine. You can also use this method to fix or patch a missing or deleted Rundll32.exe file.
Put the Windows XP CD ROM disk in the CD ROM drive
Click start, then "run"
Type: expand X:\i386\rundll32.ex_ c:\windows\system32\rundll32.exe in the Open box, change X to the letter of your CD ROM Drive. Run it.
Restart your computer
(if all else fails..)
Go to start->Run->type in SFC.EXE /SCANNOW->press Enter
Start->Type in SFC.EXE /SCANNOW->go to the top of the box, right click on SFC.EXE /SCANNOW->select "run as admin"