No, I suppose we were not talking about RegSupreme (I do not know anything about it…). Anyway, there are some links you can try:

RegClean for Windows 98 (but works on XP)
BeClean Specially the Registry Cleaning feature
But the best, you can make a download for try, is PowerTools. Very powerful registry power tools, with lots of extra options]very powerfull registry power tools, with lots of extra options. Unfortunately, it’s a shareware.

I do not have the file you mentioned: c:\windows\system32\mssmgrie.exe
I tryed a Google and Microsoft search and nothing…

I strongly suggest you this:

  1. Download avast! 4.1.289
  2. Desinstall your actual version of avast (Control Panel).
  3. Boot
  4. Run PowerTools and choose Registry cleaning. You can choose the option of a backup of the removed itens.
  5. Use Avast Uninstall for complete desinstallation.
  6. Boot
  7. Install the downloaded 4.1.289 version.

Anyway, if you need another licence key, the registration form can be found here.