I can maybe help you solve, or troubleshoot your problem. First off, this attachment, what was the name of it? Was it a .ZIP file, etc?
Also you might want to obtain some software that run through your system and see what processes are running. Print out the log and paste it here. Perhaps we can identify this problem.
In some cases, if you problem is very severe, it might be best to backup up your data first, and reinstall and start from scratch.
In a moment of tired stupidity last night, I clicked on a file in an e-mail attachment that I fear might contain some sort of spyware or trojan horse. For such a small file, my hard drive began whirring non-stop and my Dell Inspiron 1150 with XP-SP2 began to run very slowly. I ran my copy of Key Patrol, Pest Patrol, AVG Antivirus and checked Zone Alarm for suspicious entries, but quite honestly I'm not too savvy when it comes to firewalls so I'm not sure what to look for. I did what I know will save me for a short while--I disconnected from the Internet. But I'll have to get back on and want to be sure I clean our everything. I'll run Spybot next chance I get before connecting, then I'll update Spybot and run it again. But my concern is...if my suspected spyware isn't in their definitions, how can I catch it or know if I'm infected?