Some spyware is darn hard to get rid of. What Dad might want to do is to nuke the rig, set it up again from scratch, enable Fast User Switching on it, and make Restricted User accounts for each kid, or at least make one RU account for all the kids collectively. And he should make a RU account for himself too, so that even if they sneak onto his logon while he's gone, they're still unable to install software or change critical system settings.
He should ensure that he only uses the actual Administrator-class account when he NEEDS to do Admin stuff, and then log off of it and log back on as his Restricted User. If he's logged on as his RU account, he can also still exercise Admin powers by holding down the Shift key while right-clicking something, and then choosing Run As... and using the Admin credentials when needed.
I see McAfee's VirusScan 8.0 Professional (note, Professional, not standard) is set up to go after spyware/adware, and I know our VirusScan Enterprise at work will definitely go after Hotbar/Gator/FreeScratchTickets installers that websites try to feed you in a popup format. So you might tell him to get VS 8.0 Professional, it's about $42 at Newegg and is licensed for two machines per box. Spybot S&D 1.3 can't hurt as an added watchdog.
If they don't have a cable/DSL router to do initial firewalling against the Internet, they ought to get one to keep the worms at bay. The Netgear RP614 can also do URL filtering and even cut off Internet access on a schedule he can choose, to keep the little monsters under control to some extent. :evil: