Start with the basics. Run an antivirus program if they have one (make sure the .dats are current). If not get 'em a free one on the net like AVG. Run the standard freeware spyware removal programs you've seen mentioned here like Adaware and Spybot S & D. Bookmark and keep checking back to the link on the hijackthis post I added to the board earlier to learn even more from the tips there.
Search google on anything you are not familiar with. The basic spyware removal tools get rid of most of the crap and antivirus tools get rid of the critical crap.
The more you do it, the easier it get's but it can be time consuming. I've had some computers take me from a few minutes to as much as several days to clean up, and there have only been two times that it's been so bad I had to reinstall the OS.
One good tip is to have some of these tools burned to CD or a USB removable storage drive. Some people may not be able to access the internet, so you may need an alternative means of installing these tools.
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