clipped from: www.lifehacker.com From the Start menu, choose Run, type MSCONFIG, then hit Enter. In the Startup tab, run through and uncheck anything your parents don't need loading into memory automatically on boot. A bunch of these programs will be unidentifiable (though check out their file path for a hint), so when it doubt, keep it checked. If you're feeling really ambitious, use a utility like Startup Inspector to figure out what can get tossed and what can stay.
If your parents' computer is connected directly to the Internet - especially if they just upgraded to broadband this year - be sure to get a firewall running on the machine. Why? you ask. Well, a portscan will give you the answer to that question. This helpful online port scan application (Java applet) will show you how many ports on the 'rents' PC are open to denial of service attacks or worse. Without a router acting as a firewall, a computer connected directly to a cable modem is exposed to the wilds of the Internet which runs rampant with infected PCs just waiting to spread their viruses and keylog your parents' credit card numbers. The free ZoneAlarm does just fine as a software firewall; alternatively, simply enable Microsoft's built-in firewall (in Control Panel, Windows Firewall).