Desktop icons and Control Panel not working

[Bill]

My Computer, My Documents and the standard desktop icons
have stopped responding. Control Panel and Windows
Explorer also do not respond from within the Start menu.
Internet Explorer does not respond either.

Shortcuts to programs seem to work, including new desktop
icons created from Microsoft Office. Also started
Netscape from within the Programs list, and it works and
accesses the internet.

Reinstalled Windows XP...no change. Plenty of room on
the hard drive, and plenty of RAM.

Any ideas ?
..