ok I'm gonna say lets do an xp repair which keeps all your files and stuff but resets the windows regkeys, the virus may have deleted some files or the cleaning of it may have deleted some files we need, otherwise I would blame your graphic card drivers.
now doing a repair will requier you to reinstall your graphic card drivers anyways, but you can try that alone and see, but I'm pretty sure its software problem.
so its upto you, do you how to do an xp repair off the xp cd?