Virus Probs Changing Login Passwords

Okay, I got a support call today. Yeah, I do a little troubleshooting amongst my friends! Wanna fight about it? JK. Anyway, you know those stupid pop ups and such saying, "your infected" or "your virus definitions are outdated" click yes to scan. The girl's pretty wise when it comes to BS like that, ignoring those messages and such and keeping an eye on her anti virus (avast) as well.

Then all of a sudden her (avast) says trojan detected and there's nothing to worry about. THAT'S BESIDE MY POINT HERE. I am willing to bet her real virus defs weren't up to date thus leading to my point.

Some how her login password got changed and won't let her log in to her Windows profile. Does anyone have any suggestions as to a problem (other than virus problems) and may be some links to some support. I never heard of this happening I'm sure it does all the time, but not to me.

Last but not least, how could I get around the password login problem?