Applications/icons not responding

Compaq Presario bought with win98se preinstalled. Now with windows 2000 advanced server. AMD K7. 256MB ram. sp2 installed.

after about half an hour to one hour of logging in all icons become inactive and don’t respond to mouse click. only icons next to time logo at extreme right hand of the task bar respond OK. Also, ATI TV launch pad can be activated. them same with ATI DVD, etc. but not any other sound icons like real audio etc. I have disabled PoweManagement, screen saver, wallpaper…no use. my remedy is to log off and login. then everything is OK for another hour or so. I heard you are of great help in dead end situations such as this one. Can you please help?
Thanks
Cyrus