This is a real common problem.
Try this first.
Click Start | Click Run | Type or paste the following line:
regsvr32 /i shell32
Click OK.
A tip from David Candy.
If that doesn't fix it, see these...
Search Companion Starts If You Double-Click a Folder or Drive
http://windowsxp.mvps.org/searchwindow.htm
Fixes the problem where Search or Command Prompt opens
when double clicking a folder © Doug Knox
http://www.dougknox.com/xp/scripts_desc/xp_folder_open.htm
Search Companion Starts If You Double-Click a Folder
http://support.microsoft.com/kb/32118
Search companion opens when you double-click a Compressed (zipped) folder in
Windows XP
http://windowsxp.mvps.org/zipverb.htm
--
Hope this helps. Let us know.
Wes
MS-MVP Windows Shell/User
In