I was hit by a trojan. I ran several programs to make sure I got rid of it. I ran TDSSKiller, MalwareBytes, RogueKiller, Adwcleaner, Spybot Search & Destroy and my antivirus - Avast. I ran the disk defragmenter and it said I did not need to run it. It was okay for a few days. Then I started experiencing slowdowns. The computer was crawling and I couldn't even type in words. This happened while I was on a dial-up connection and on a wi-fi connection.
Dell Latitude D610 laptop, Windows XP SP3, Dial-Up connection
What can I do to further diagnose this?