Desktop Web Page Activation

Installed systems:

Windows ME
Windows XP Professional
McAfee Virus Scan online

I am unable to activate the web page settings on the
display/control panel to change my wallpaper backgrounds.
When I click on anything to change the background, my
computer freezes up (the timer icon comes on) and I end up
shutting off the power to restart my computer.

Am I missing a link somewhere? This only happened
recently.

Thanks.