for spyware/malware/worms? http://www.ewido.net/en/onlinescan/
KAV also has one, but if main AV isn't seeing anything, the same online wouldn't either. Just a 2nd opinion better safe than...nothing gets everything and Adaware (SE? or 2008?) is/was mostly concerned w/ adware.
When you say Yahoo! Mail, do you mean web based and accessed via your browser or was this something included in set up from your ISP & accessed via OE? Was KAV supplied by ISP or did you purchase/get on your own??
Yahoo, quite awhile back, changed from including free KAV to McAffe, I believe, and many users never saw the notice & for months thought their KAV was updating when in fact it wasn't!
In my case it started out as Rogers(ISP Cable) own mail server (O.E.), but then got sold out to Yahoo! mail, so now mail goes thru Yahoo (via Rogers out & in) along with the problems Yahoo is subject to. (Hint: Rogers is soon to revert back due to massive customer complaints).
It just seems like there is an un-sent mail trying to get out. Either you had one left in cue to be sent & never was OR >>something! is trying to access your mail system independent of you (TROUBLE).
If you go via O.E. then there are going to be 2 cues (waiting lines involved) one in OE Folder & likely 1 in KAV's folder. You could look via My computer>C:>Program files (KAV) or Windows>OE and delete any mail you find in either cue folder.
Normally, mail goes out OE but it then is into KAV for inspection before being forwarded to final addie. At least that's how it works w/ AVG. Since I don't have KAV, I'm speculating on this.
Have you a system restore point before this started available?
One other thought, perhaps try running a SFC in case a bad bit of script has corrupted the OE or XP paths for mail. Sometimes, things seem to get corrupted for no apparent reason....
Ideas are getting thin ...hopefully another has seen this before.
Mark is extremely knowledgeable (unlike myself) & it'll be a humdinger if it stumps him!! Good Hunting!!