I feel your pain. I had a AMD K62-400 as well, and while it was zippy in a lot of applications, it was slow going in Aces High. Frames of under 20 consistently...and if you really wanna slow down, wander down near smoke or ships. <sigh!>
But...I upgraded to a new motherboard and an Intel P2 450 for under $150 a few months back, and I just replaced the P2-450 with a P3 550. Im running 384mb of RAM and a Voodoo 3 3000 and frames are at 30 or higher, most of the time.
Get a zippier CPU, say an Athlon if you can swing it and be prepared to grin! The only reason I have the P3 now is my friend needed a matching P2 450 for his NT Server and he made an offer I couldnt refuse (aren't trades cool? Just wish he had an Athlon to barter with!).
I've been eyeing the video card discussions here, trying to eek out some more FPS. ATI Radeon 64 seems to be getting the most nods?
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Paul J. BusiereAces High Arena handle: BD5Pilot
http://bd5.checksix.net BD-5 "T" (TurboProp) 90% complete, first flight in 2001 (We hope!)