I used to have a similar problem. This windows cannot find rundll.exe
solutions summary page helped me. Whiel its beginning contains some advettising fluff, skip it all and scroll to the bottom. The you'll find what htey call a manual slution methods and it worked for me.
Other possibility if that you have your real rundll.exe file corrupted. In suhc case I recommend you to run sfc.exe /scannow command from Start->Run dialog. It will search for corrupted files and recover them from your Windows CD. Good luck!