FS Real-time halting FS

I had previously a DELL 4100 on which the FS was running O.K. if not well (12 frames/se down to 4 when lot of resources were needed).I have bought a new PC DELL 8300 2.6GHz 800fsb with a 128Mb Radeon 9800 graphics card. Good is it not?Well something strange is going on in this PC.If I start FS2002 I get a frame rate around 32 It seems to keep that value as long I do not add anything else to it. (The plug in sceneries of FSGenesis are installed in the FS.)First scenario: I start FS Real Time only FS and FS Real time active; no other program running except the load of usual stuff like logitech, sound, Norton AV & Firewall (needed for later internet access while flying). I stopped all programs which I have control over.After a while (20 to 60 seconds) the frame rate drops dramatically BUT progressively. Until it reaches ONE frame / sec. No use to tell you what FS looks like at that moment. If I stop Real Time the frame will SLOWLY go up to... 4 frames/sec. (shifting between 2 and 4) Then much later up to 10-13. Oh the plane is sitting still on an airport with engines stopped.When the frame is down to 1 the WHOLE of the PC is very slow. Getting into WordPad takes lot of seconds instead of being almost instantaneously.To get back to the PC normal speed for other tasks I must stop and restart FS2002 to get back the 34 frames.Second scenario. After restarting FS2002 I start an Internet connection. During the init time the frame drops to 12 for a very short time then it climbs back up to 34. While working with WordPad for this message it drop to 8 until it returns to the FS screen.Now I start ActiveSky. During the initial loading phase of weather from Internet it frame slows down to 24 and climbs back up to 34 when ActiveSky is dormant in the background. When flying the frame rate keeps its 34 level.So it is FS RealTime that slows down the PC. Maybe it did it also on the old PC but not as dramatically.Luckily FS RealTime is not really needed. It is just good to have it. So the FS time stays synchrone with reality.But has anybody an idea what is going on? And therefore what can be done to improve performance while using FS RealTime.Roger