How to Unregister DLLs

Dynamic link library (DLL) files are basically a collection of programs which are called upon by a main (executable) program. In order for a DLL to be usuable it has to be registered so that the main program access it. In the case of a computer infection, the malicious program will put malicious DLLs onto your system. Therefore to fully remove a malicious program from your computer you also need to unregister its DLLs. However, in most cases you should not delete the DLL because the malicious program may simply use a system DLL for some of its functionality. Here are the necessary steps needed to unregister a malicious DLL:

In the command prompt window use the command CD to change the current directory to point to the DLL’s location. For example, if the DLL is located in C:\Windows\System32 enter cd C:\Windows\System32 at the command prompt as shown:

regsvr32 -u <filename>.dll

where <filename> is the name of the file.

More information see:
http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/regsvr32.mspx

http://support.microsoft.com/kb/q249873/