Is there any major differences between that old Windows CE 3.0 and this new Windows 2002?

I have MFC program working fine in old 3.0 but for some reason it doesn't work in 2002. I was thinking that if there is some differences in MFC runtimes or something. Any clues anyone?

And is there any differences in kernel? I read that they both use same kernel but you never know when it comes to MicroSoft.