All of a sudden several applications won't run anymore. The ones I've noticed so far are Defender, Spybot, and Spyware Doctor. They start as if they are going to run, but then they just never open the window. I've run a complete virus scan using Norton. Thinking it might be a registry issue I also ran a registry checker but no problems were found. Any help is appreciated.

Can't say it sounds good so far. Ideas to try are a system restore to a time it did work. Might try norton's or others online av. Might try MS's live beta products. Might have to see about a rootkit tool. Run the MS malicious program from downloads area.

That sounds like a baddy alright. The first thing it does is shuts down the programs that can remove it. Then probably duplicates itself to some good program to fool other spyware programs. The issue here is that generally speaking these types run through a service proccess. You need to run your AV in safe mode and do a complete system scan. In The Matters Of Style, swim with the current; in matters of principle, Stand Like A Rock

If it's Microsofts Defender beta version you have installed you might try to uninstall Defender before going any further. In my case it blocked some programs from accessing the HD and from working properly. You can always reinstall Defender.