In your description, I didn't see anything that said what activity causes the crash. Does that mean that you can load Aces High then walk away and it will eventually crash? If it doesn't crash there then does it crash only after you are logged in? That would indicate something that only occurs when, perhaps there's network activity going on...or activity on the screen or sounds. Does it crash in offline mode? If it doesn't crash in offline mode then that would narrow it down to possible issues with the NIC card...???
(you don't have to answer all these questions in the forum...you can ask yourself these)
If it crashes all the time randomly with nothing in common, even if the computer is sitting there idle then I would suspect a thermal or other hardware problem (such as power supply). If random lockups are happening while you're not using the PC, regardless of the applications you're using, then try this: Run the computer in Safe mode for a long enough time to determine if the crash happens. If it doesn't happen in safe mode then that pretty much rules out a problem with the CPUs overheating. (you see I once had a CPU overheat prob and it locked up no matter what I was doing, even idle). If the crash doesn't happen while in safe mode then that seems to show that the crash is related to one of your devices. Try to use an alternate hardware profile. (i.e., Control-Panel|System|Hardware|Hardware Profiles), and disable various things, such as the audio or network NIC driver and experiment with different settings. See what happens when you run Aces High with no sound driver installed. See what happens with no NIC driver. Of course you can't substitute out the DirectX drivers, nor can you run AH in safe mode. But this might get you started on narrowing down what component is needed in order for the problem to happen.
Hope I didn't patronize too much, I have no idea what your expeience level is.
I know how frustrating intermittents are so it might take some time to narrow it down but try disabling stuff and wait to see what happens. If you have Windows XP you can use the system-restore facility to save your current system before you mess around with it.
Oh one more thing, then I'll get going...
I had a recent problem with Windows 2000 where I had to reinstall DirectX and somehow I messed up my system so badly that I could not uninstall DirectX or clean it out . I had to reinstall the system to fix it. Hope yours isn't that dire.
Good luck,
Barfo