Jane's USAF works flawlessly on Win98SE.
It has issues with WinXP that cannot be fully resolved without a patch that will never come.
Those that are loyal to Jane's USAF either use a dual-boot machine, or live without the Quick Mission Editor (all of the other problems can be worked around one way or another).
For extensive help from those dedicated to Jane's USAF, I recommend SimHQ's dedicated forum which will hook you up with anything and everything you need for Jane's USAF:
SimHQ Jane's USAF Forum For the majority of downloads available:
McFly's Hangar This sim is still under development by the community there:
New models, terrains, even an upcoming SuperPro 2 patch that supposedly improves the flight models dramatically.
Personally, I moved on to TK's Strike Fighters Project 1 since it models my favorite aircraft (the F-4 Phantom) better than any other flight sim. However, SFP1 does not yet fully support hi-tech weapons and avionics nor does it come with a mission editor, so many people still play Jane's USAF.