Rundll32.exe is a process which executes DLL’s and places their libraries into the memory, so that they can be used more efficiently by applications. This program is important for the stable and secure running of your computer and should not be terminated. Check and ensure that the particular rundll.exe is situated in the System32 folder. If so, it is the legitimate Microsoft process, else it could be a virus.
The following is, primarily, based on the fruitful discussion at TechNet, and the important points have been culled out from there and presented here.
Windows Host Process Rundll32 has stopped working
If you get this error message frequently, here are a few troubleshooting steps you may try:
1] First and foremost, ensure that your Windows is fully updated.
2] If you get the error when opening folders that contain video files, turn off thumbnails view and see if it helps:
Open Control Panel > Folder Options > Always show Icons, Never Thumbnails
3] Try to remember, when did this error start popping up.
Was it after installing a particular program? Was it after installing, say, Nero ? if yes try this:
Open Computer > System Drive > Program files > Common Files > Ahead > DSfilter. Rename “NeroVideoProc.ax” to say “1NeroVideoProc.ax”. Also rename “NeVideo.ax” to say “1NeVideo.ax”
Maybe you could update or uninstall Nero software and see if it helps.
4] The Intel ViiV software and the K-Lite Codec Pack too are known to cause this problem. If you have installed any of them, update them or uninstall them and see if it helps.
5] Follow these steps to try and find out, which software is causing this issue.
Run msconfig to open up the System Configuration Utility window. Click on Services, and check in the “Hide all Microsoft services” check box. Click on “Disable All” button.
Now click on “Startup” tab, and then click on “Disable All” button again. Press OK button and then “Restart” button on the following window.
Effectively, you have turned off all non-Microsoft services and start ups.
If the issue is resolved, open System Configuration Windows again and then enable all the services from Services tab and then check the issue after restarting the computer in the same way as mentioned above disabling one service at a time.
6] Turn off Data Execution Prevention and see if it helps. But remember that this is a security feature that is there to help protect your computer.
7] Run the Microsoft Windows File and Folder Troubleshooter and see if it helps.
This way, you will have to enable/disable services and start ups to narrow down on the culprit. Agreed, this is a lengthy and painfully boring process, but it will help you identify the culprit.