cpu usage @ 100% – winexplorer problem

When i use a windows explorer window, my cpu usage goes to
100% and doesn’t come down ubtill i close it with task
manager. also, the little green systray icon for cpu usage
that appears while task manager is minimized is no longer
visible after i force-quit explorer.exe through task
manager.
This is on a thinkpad a21m with power constantly connected.
I have WxinXP SP-1 installed.
Please suggest, my machine is useless without the ability
to browse folders.