On one of our IIS servers, Explorer.exe has ceased working. You can double click on My Computer, and Explorer says "Unknown or invalid argument." This makes absolutly no sense. We do all our file work from cmd.exe on it now. It's very odd. Sure a reboot would fix it.

Had this problem with some NT machine at the previous job I had. Took the whole day to find out what caused it (as Im not _so_ familiar with all the NTs registry stuff). Anyway, after browsing through some hughe books about Windows registry, the problem was solved. Im sorry I cant remember anymore the exact field that caused the problem but I think you could find it by comparing the registy of the server to some similar server you have. Sure it takes time..

Dont know however what originally caused the change to the registry.