Thanks for your replied slarty...

The reason I tried to ugrade kernel 2.5 is just for testing (yupe I'm very sure kernel 2.5 is unstable ...I agreed with you)
2.5 is the unstable series. Currently it's passed its feature freeze, so theoretically it should be more stable now. I've built a few 2.5 kernels so far - about 50% didn't build and a few of the ones that didn't build didn't boot.
So you've already tried too.....mmmmm might be not going to be work for me..

If you must run 2.5, do it on a separate disc (or machine) where you have *no* data that you remotely care about, and on a machine you don't mind crashing, failing to boot etc. Don't mount any local discs you care about read-write.
Yupe ..I've got one box special if I wanna play around with Linux...so I don't mind if crashing my box..( it happened many times....well...mmmm that's part of my learning..*nix here..)

In answer to your original question: you probably need to install the libqt2-devel package from your original distribution. Or it might be a later version. Or something. Anyway it should be included on your current distro if it's vaguely recent. If your current distro is out of date, don't attempt to build or install 2.5 as it may not work anyway.
I'had built that kernel on current distro.....and the libqt2-devel already in it.
I guess you alright slarty..maybe I shouldn't built kernel 2.5 (I can't wait for kernel 2.6 )..
But I will try again today (all day ) to figure out this kernel....maybe I am lucky

ps: I've been using non graphical tool ..to built kernel 2.5....I can't get xconfig cause I need QT