Wife's laptop WiFi will not stay connected to router. I think

[jim.mar]

My wife has a HP9000 laptop running Windows XP.   She is using WiFi connected to a Netgear wirelss  router  in my home network.   My base computer is a desktop running Windows 7 64 bitand is connected to the router via ethernet cable.   For a couple of years now this system has been working satisfactorily....but...    

PROBLEM:   When she clicks on internet explorer, the laptop connects to the internet and tries to  bring up Yahoo or Google home page  a message appears:   "Internet explorer has encountered a problem with an add-on and needs to close". 

the name of the add-on is       yt.dll

If I check my internet connections it appears to have disconnected.
Can any one advise me of  the problem??

NOTE:    Sometimes she can get google but cannot access any of the web sites in her favorites list.

[jim.mar]

OOOPS my bad.  Her machine is running VISTA.

[Geek-9pm]

Uninstall the Yahoo Toolbar.

[jim.mar]

Thanks for answering.     OKAY I un-installed Yahoo tool bar which did change the way it acts but did not fix the problem.  Still cannot access any of the sites on favorites list.