htmed.dll error during MS Service Pack 5 installation

While installing MS Visual Studio Service Pack 5, I got the error message “htmed.dll was unable to register itself in the system registry”, after which installation was not successfully completed. I installed the service pack after installation of MS Visual Studio 6, during which I encountered a “Setup Was Unable to Create a DCOM User Account” error, which caused unsuccessful installation of MS Visual Studio 6.( I managed to address the DCOM error by re-installing Studio 6 without the Visual Studio Analyzer.)
De-installation of MS Studio 6, erasing of remaining htmed.dll files, and subsequent re-installation of MS Visual Studio 6 and Service Pack 5 did not remedy the htmed.dll error. Is there anything else I can do?