Out of the blue sky, I can no longer use SEARCH in WIN XP Pro. The search input window comes up but is blank (no entry fields for file name, search locations, etc. This is a sorely missed function. Short of re-installing WIN XP and loosing a lot of information I am at a loss about what ti try. What would I need to RESTORE from an old backup to get this window function back?

If you just reinstall Windows (not deleting anything) over the previous Windows (this means installing it to the same directory when it asks you where to install it to, probably C:\Windows), you shouldn't lose anything.  That may or may not correct the problem.  If it doesn't, you will have to do something more drastic.