Let's run one more scan and if that doesn't show anything you should go to the XPHelp section of this forum and see if they can help as this is the malware section.
Try running this:
Download
http://www.bleepingcomputer.com/files/winpfind.php
Extract WinPFind.zip to your c:\ folder.
Please print these instructions as you will be going into safe mode.
Reboot your computer into Safe Mode by following the following steps:
Reboot.
When the machine first starts again it will generally list some equipment that is installed in your machine, amount of memory, hard drives installed etc. At this point you should gently tap the F8 key repeatedly until you are presented with a Windows XP Advanced Options menu.
Select the option for Safe Mode using the arrow keys.
Then press enter on your keyboard to boot into Safe Mode
Then open c:\WinPFind and double-click on WinPFind.exe. When the program is open, click on the Start Scan button to scart scanning your computer. Be patient as this scan may take a while. When it is done, it will show a log and tell you the scan is completed. Reboot your computer back to normal mode and and post the contents of c:\WinPFind\WinPFind.txt