My yahoo rant:
I have an unsupported opinion: stay away from yahoo anything. I had to trash a pc after so many reinstalls due to all the crap (spyware/malware) I would pick up from using yahoo mail and having my site hosted on yahoo (a few years ago).

I had been on a tirade about yahoo for years before finally hearing a blurb about them being sued for subscribing to spyware and malware sites in order to "up" their page results for their advertisiers.

Some options you may use instead of the popular programs:

A really good chat program that enables users to use yahoo messenger, aim, icq, and msn - all in one interface: Trillian - http://www.ceruleanstudios.com/ - you don't get any of the extra adware or spyware with it.

Totally agree with the trend micro online scanner! As long as you are still able to download it. Make a habit of using it weekly at least.

I use Google for a lot of things, including gTalk - and have never had any issues related to spyware or adware.

Free spyware remover - Adaware: http://www.lavasoftusa.com/

Paid Spyware remover - Spyware Doctor: http://www.pctools.com/spyware-doctor/

Registry Mechanic (love this!) http://www.pctools.com/registry-mechanic/

---Stay away from search bars, etc. You don't need them - and try Mozilla Firefox as a browser too. I use both IE and Firefox.

Do you know how to disable your startup items and start in safe mode?