If you've received this error and your system is using the Realtek HD Audio Control Panel, you might be scratching your head just as I was. After a bit of research, I found out that this error was most likely caused after installing Microsoft's security update 925902 (MS07-017) and security update 928843 (MS07-008).
The problem is that the Hhctrl.ocx file and the User32.dll file that is included in each of these security updates have conflicting base addresses. The resulting error occurs when the program loads the Hhctrl.ocx file before it loads the User32.dll file.
The error may look like the following:
Rthdcpl.exe Illegal System DLL Relocation
The system DLL user32.dll was relocated in memory. The application will not run properly. The relocation occurred because the DLL C:\Windows\System32\Hhctrl.ocx occupied an address range reserved for Windows system DLLs. The vendor supplying the DLL should be contacted for a new DLL.
You can download the fix directly from Microsoft Here