Originally Posted by Unregistered

Cheers for the solution, did exactly as you instructed.

Changed the SHELL value to "windows.exe" only.

Checked the processes in Task Manager and "lsass" is running after start up.

All seems to be right with the world :-)

This happened to me immediately after installing Nero 7 and all the relevant updates.

Nero does have some software that integrates with explorer.exe, I was wondering if this contributed to the problem.

I definitely found no virus, nor has any been deleted recently. The other registry keys mentioned were clear or do not exist in Vista.

Anyway - CHEERS!