I tried a couple of different ones but deleted them plus the one on XP and then tried this free and tiny (no install) 46kb zipped Catalogger/File Finder made by Robert Vasicek, called Cathy - I bet there are none faster/simpler/better - I dug a bit and tried to find a file using XP called fxsocm.dll - it found 2 editions of that file in 2 different locations regardless of how many times I tried but Cathy found 3 in 3 different locations instantaneously. http://www.mtg.sk/rva/
I rarely search for files, but for Windows i find locate32 very good. http://locate32.net/content/view/14/26/