Well after running Norton and removing the infected file, the computer still acted up, so I tried an Ad-Aware Lavasoft scan. Froze, so I rebooted. Before loading up windows, the computer did a System Check, and replaced an invalid security ID with the default one. Then it loaded back up. After disconnecting the internet again, I ran Ad-Aware Lavasoft again, and when the scan was through, it detected another trojan. Removed it, rehooked the internet, and so far it has been running fine.
I am not 100% sure yet but I think the problem's resolved now.