A Virus or Hacker as changed my Desktop!

Hi All. This is my first post so I'll try to include all relevant info.

Last night while working on my pc a window popped up similar to the Blaster Virus "NT Authority is shutting down your PC". It gave me 45 secs then restarted my PC. Once restarted it changed my destop theme to Windows classic and removed any other choices from the windows and buttons drop down list.

I've run scans with AVG, Trend on-line scan,

Call me strange, but I quite like the standard XP colour scheme and buttons. How do I restore it. Please help.

My PC is a fairly standard one:

Windows XP Home SP2 - fully updated, AVG, MSAS, Adaware, Spybot, Spywareblaster - All latest versions and fully updated,
Athon 64 3000, 512MB DDR400, 256MB 9600 pro, 3COM Router - Firewall on,
120Gb and 80Gb Hd's

 

Right click on desktop

Properties
Themes
Windows Xp


Then click on appearances

Windows and Buttons should be Windows XP.

 

Thanks earlthemailman,

But that's the first thing I tried. the "Windows XP" option isn't there. Neither is any other one. You can only chose "Windows Classic style".

This may be unrelated, but I've just noticed that sound is being played in "slow motion". This is really weird.