Spy Sweeper dectected SYS Keylogger Pro. How can I make sure my computer is completely free of this?

My operating system is Windows XP, Media Center Edition, Version 2002 with Service Pack 2.
Internet connection = cable.
Router = Microsoft Broadband Networking Wireless Base Station, MN-700
Cable Modem = Motorola
Security Software = Norton Internet Security 2007, Webroot Spy Sweeper and Webroot Window Washer

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This morning I ran Webroot Spy Sweeper which detected the Keylogger . I quarantined the Keylogger. I then accessed Turbo Lister 2, which I had knewly installed and briefly used last evening from Ebay, I thought that might be where the keylogger came from. After accessing Turbo Lister and closing out of that program, I ran Spy Sweeper again, which detected the Keylogger. So, I uninstalled the program through the Control Panel. I ran Spy Sweeper again, which did not detect a KeyLogger. I still have the KeyLogger in the quarantined section of the Spy Sweeper program.

What else should I do? How can I make my computer is clean of this? Help!!!!!