explorer.exe? or another problem?

So I've got a Dell /w XP Media Center. The taskbar continually fails to appear. Strangely enough I've never had a problem with icons. Taskbar is the only problem as of yet.

I did have a few troubles with Microsoft Office 2003 Powerpoint, slowing up certain features weren't working properly, at the same time I first lost the taskbar. So there's several of us who routinely use this PC, and someone used a system restore point from a few weeks back to solve the problem. Only temporarily.

Well the taskbar is MIA again. And as of yet no other problems.

I can get to taskmanager no problem. I can run searches, search for files in My computer.
Anyway I checked running processes and only one instance of explorer, so I stopped it and ran another and still no change. Restarting changes nothing.

I have Avast on there despite the fact the computer has no internet access. And it's detected nothing.

I did install Audacity, and a MP3/wav converter (the only downloaded programs) however the uninstalling of both changed nothing.

Any ideas?

 

Any body? Even if I could get pointed to some diagnostics that might rule somethings out. I'm at a loss because this computer has no internet access, and no one who routinely uses it has enough knowledge or equipment to load programs or files from an outside source.