Ctrl+f does not work in xp

Hello:

I have windows xp in my computer. Ctrl+f used to work before in professional to find files & folders from desktop or windows explorer (not from application, it is fine with application) but now with xp, it does not work.
I am expecting it to work like-without opening any program or window just press ctrl=f and the find window will open.
can someone help?
Thanks