Having been persuaded to again try Vista Ultimate (dual booted with XP Pro) I loaded up a fresh Vista install on a clean hard drive. This time I decided to load FSX/SP1 on the clean install before doing all of the other things I needed to try. The result...In my standard "test" flight comparison, the average FPS with XP was right around 48. The same situation with Vista gave an average FPS of about 12. Not a very scientific study, but the difference is so striking that a few FPS one way or the other hardly makes any difference. Has anyone else seen this dramatic a difference between the two operating systems? I've looked at all the "usual stuff" (drivers, concurrent services, AV, etc.) but I don't have a clue as to what's really going on. Not that I'm going to look much further, but if anyone else has seen this large a disparity I'd like to compare notes.DougP4 3.2E @ 3.680 (1.385 vCore - 230 FSB)Asus P4C800-E Deluxe (BIOS 1023)3GB Corsair XMS-3200C2 (2-3-3-6-2T)1.5 TB of Western Digital HDDATI X850XT PEA-Open 1648 AAP RipperPlextor 708A WriterEnermax 431W PSUInwin Case

In my experience, you might see a small deviation in performance depending on hardware, drivers, and configuration, but no way you should be seeing a huge 4:1 difference. BTW, not that it will solve that kind of huge disparity, but have you applied this update?http://support.microsoft.com/kb/932246

My framerates were almost identical between XP and Vista Home Premium.Steven.

Same here.

No I haven't tried it. But, then again, I've never thought of FSX as a "legacy" game :-) . Doug