My father's computer was infected with somekind of spyware/adware and I tried various things to remove this nasty bloodsucker... after hours of trying everything under the sun, simply installed Firefox... that's the only thing that worked!
IE seems to be what triggers the ads. Firefox doesn't. I didn't try Opera or others but they might work similarly.
Orlando Todd, Firefox dinna fix anything. It's simply not impacted by the particular infestation on that machine. The spyware is still there and will reappear if IE is ever used again.
Using spyware removal programs like Ad-aware and Spybot Seach and Destroy and Spywareblaster will knock out the bugs. Continuing to use them regularly is a very good idea as well, especially on shared computers.
I ran Ad-aware and even through some extra steps disabled the recovery, ran it in safe mode, and it never got this one. I agree it didn't get rid of it, but by using FireFox, the ads don't get triggered so.. a fix of sorts for those who give up.
I may try running the other you mentioned and I didnt try Yahoo's toolbar one yet, but unless Firefox has a problem with sites he visits, I see no problem in letting him continue with FF.
You really should get rid of it. No telling what it might be "timed" to do.... And of course, you can't guarantee he'll ONLY use FF - a lot of people start out with good intentions and fall by the wayside eventually.
It usually takes a variety of programs to completely clean a bad infestation. Use all of the ones others have mentioned.