Have you searched using More Advanced Options? By default, XP does not search hidden folders (bloody stupid).
In Search, after selecting Files and Folders, there's an drop down for More Advanced Options, and a check box for Search hidden folders (System folders should normally be checked by default).
If that doesn't help, ensure that your Windows Explorer is set to show Hidden and System Folders in the Folder Options list, then search manually through every single folder, in case the file extension is not one you recognise.
Bearing in mind that photos and vids are big files, you could narrow the search by checking the size of each higher level folder - if it is very big, it's worth searching, and don;t bother if it is small!
Another thing you could try is to do a DIR /S (see DIR /? for other options - sort by filesize or extension) piped to a text file which you could then trawl through, as it might be quicker than opening each file individually.
SD