there is no reason not to have an antivirus product on your system as you can get a decent one for free click here install it, update it and run a full scan deleting all it finds. if you have windows xp or windows me then disable system restore if it finds anything and run a full scan again.
check for spyware with these free tools click here click here do the same as above. install, update and scan then delete all. you owe this to the rest of us users. its irresponsible not to use these now days.