Bizarre search for files problem?

Using win 2000 (sp4)

When I try to find files using the "search for files or folders" it will not
work for multiple drives!

For example, by default all drives are shown in the "Look in" dropdown,
typing in*.doc and clicking "search now" returns immediately saying "search
complete. There are no results to display" - if I put in just "C:" it finds
some!

Any ideas? this use to work & I have absolutely no idea why it suddenly
stopped!

thanks

harry