Everything will probably be okay. Of course no guarantees, but most all software within the past few years will work. Some software may require a little work with the Compatability Wizard to get working correctly. This extra work is well worth it to get away from a 9x based system. And I have personally found that many DOS based games (Wolfenstein 3D, Doom, Redneck Rampage) have worked, after some tweaking with the CW.
[EDIT]Anything is more stable than Windows ME. Windows XP is extremely stable.
\Dan