Windows XP SP3: Only desktop wallpaper. No start menu, no icons, mouse works but nothing to click on!

Start menu doesn't work. Taskbar doesn't work. When I ctrl-alt-del, the menu comes up but when I click on taskbar nothing happens. Taskbar was working before and I was able to run trendmicro online and Ad-aware. Ad-aware found 2 files and said they were trojan downloaders. Can't recall names, I think one was mwabid.exe or something similar. I deleted them both and when I rebooted, It ended up like it is now. All the same except now I can't even access task manager. I guess viruses are still there because even though there is no screen activity, modem flashes like crazy.

Tried safe mode, same results. Tried to boot to Windows disk, nothing. Goes back to bare desktop. Can't get to command prompt either.

Help!!!