Fluctuating FPS !

Im not usually a fps chaser, as long as the sim runs smooth I'm happy. However, as I have been suffering massive drops in fps in spot view just lately,like from 18/27 to 2/10 I've been putting the counter on. Tonight, I changed the drivers from the 44-03 to the Omega 45-23a. The fps went up quite a bit in spot view, so I'm well pleased with that, 19/27. My question is this-- in spot view, no weather, so I have a clear blue sky, looking up at the aircraft so that the picture stays constant the fps counter is constantly moving between those numbers, like 19-24-18-26-27-20-23 etc. I would have thought with an unchanging scene the fps would stay steady. Any comments as to whether this is normal-or not- would be greatly appreciated. I'm itching to buy fs2004 but, after reading a lot of posts on that subject, I feel I need to get something(but what?) sorted on my machine first. I would point out that this drop in fps only happens with the aircraft I use the most, the Posky & Meljet 747-400s mated to the PSS PW sound set. I have the fps locked at 30 and in cockpit view they stay around 25/30, but, again, always rotating between those figures no matter where I am.Regards,Russell.AMD 2400xp+DX 9-0bBios Phoenix-Award v6.00pg512 DDROmega 45-23a driversGF Ti4600 128mbVia Hyperion V449vp2