I think he installed it with a vista home DVD he had
Does your Vista installation sound legit? For instance, do you have any problems with updating Windows?
How long ago was Vista reinstalled?
What AV and firewall do you use?
Is this desktop, or laptop? What's the brand and model?
How do I know how many sticks of ram I have / start with only one?
Have you added any RAM, or is the computer in its original state?