1) what operating system and service-pack?
2) do you have antivirus software, and if so, what brand & version?
3) how do you connect to the Internet (cable, DSL, dial-up)?
4) got a router, or no router?
5) does this correlate to anything, such as installation of new software, or clicking a weird link in an instant-messenger program, or visiting a new website of a risky nature, or ???