1. Run Windows in Safe Mode. Restart the computer. At reboot, press the 'F8' key repeatedly. Keep tapping 'F8' until the Windows Advanced Options menu appears. From that menu, select 'Safe Mode No Networking' and press 'Enter.'
2. Run antivirus and antispyware scans. This may take several minutes, depending on the size of your hard drive. Delete any malicious programs that are discovered. Reboot the computer.

3. Insert the Windows system CD or OEM system recovery CD after Windows has loaded.
4. Replace your old rundll32.exe file. Click the 'Start' menu and select 'Run.'
5. Type in the 'Run' dialog box (without quotation marks):'expand X:\i386\rundll32.ex_ c:\windows\system32\rundll32.exe' with 'X' being the letter of your CD drive. This will install the original rundll32.exe file that came with your Windows software. Reboot.