Geek Help

Hi! As if this week wasn't fucked enough (insurance people think I don't exist! Medical assistants are rude and classist! there's FAKE GRAVITY pulling me in weird directions! I HAVE TWO PAPERS DUE and apparently I need an MRI...) - I seem to have picked up a weird Trojan! I know, I know, those filthy corners of the internet that you have to frequent in order to get the skinny on Satan...

So, I ask for assistance, Oh Ye Mighty Powers of Flist!

When I open IE, I get infinite amounts of popups; at first they were for porn; they have now devolved into ebay ads, verizon ads etc. Then the browser closes by itself for no reason. I have installed IE 7; this did nothing to help. I'm using Firefox now, which seems free of the popups, still has the occasional popup though with much less frequency, but I am concerned about infection in the innards of the machine.

Thoughts? Advice? I am poor and un-techsavvy, and would much appreciate any pearls of wisdom you lot might have to offer...

ETA: Thanks so much to anyone who offered help & advice, especially visitors from rm's flist. New Problem: The virus/trojans/malware is preventing me from running any of the setups for the spyware/virus scan etc. that I'm trying to downlad. It's just stopping in the middle. Also, it's giving me fake alerts about spyware that purport to be from Windows, but aren't. I'm beginning to think I'm truly screwed.