Voximation ... I realise this happened after you fixed spydawn but try these.
1. Have you tried installing a fresh copy of explorer. exe from, say, your master disk?
2. You may have too many things in your startup. Boot to safe mode and disable some items. See if the machine boots into window normally again.
3. Here is a troubleshooting tutorial that may help ...
http://www.techspot.com/vb/showthread.php?t=8356
Hope something here helps.
If not there are other things to try but please post a HJT log in normal mode, if you can, so we can at least check to see if there's anything obvious lurking (despite your own confidence that there isn't).
OJ