Zip file support doesn't work

For some reason, my .zip files are not recognized as such. I tried

regsvr32 c:\windows\system32\zipfldr.dll

but I get the error:

"The module "c:\windows\system32\zipfldr.dll" was loaded but the entry-point
DllRegisterServer was not found. Make sure that "..." is a valid DLL or OCX
file and then try again."

Is there anything else I can try. I can right-click on any file and pick
Send To->Compressed (Zipped) Folder and this creates zip files. But I can't
open these, or any other zip file.

Thanks for any ideas!