I think you're being just a tad overreactive there. Your CPU will not be tremendously inundated with superviruses the instant you connect to the internet. Trust me. I've built many computers and installed many copies of WinXP. Never had a problem. The only way you can get a virus like that is if you get a weird email with an attachment that you proceed to open w/out knowing its contents. Otherwise, you're fine.
If he is not on the latest patches, he WILL be infected with some sort of malware within minutes (or seconds). The best thing to do would be to ensure that the built in firewall is enabled prior to connecting to the Internet.