A bit of a sorry tale

This may turn out a bit long - hope you can bear with me. It's a prob that's driving me nuts. When FS9 first appeared, I, like other multi monitor users, had a problem running in windowed mode, whereby I got a regular brief stutter approximately every 13 seconds on sound and graphics. When I went to full screen mode, this prob disappeared. However, there was a reduction in fps as well as other difficulties in setting up panels on other monitors. Despite this, I've stuck with full screen and with one or two slider compromises it has all worked reasonably well. Then a couple of weeks ago, during a nasty storm, my house was hit by lightning - the resulting surge fried much of my main 'putes and did some damage to two other machines on my small network. It took me about 12 hours to physically rebuild the system; it's taken the best part of two weeks to get my flight sim set up in order.Most things I can get around - luckily my hard drive survived so all my original fs settings were in place. I also managed to repair my old vid. card - a Gainward Ti4600. The one issue which is driving me mad is this. My old system was based around a P4 2.8, the new one has a 3.2 gig processor, with one or two other items designed to increase speed. Normally I have my frame rate locked at 21 and on my old system in window mode, with panels opened on the main and two other monitors, I would get about 19-20 fps. When I went to full screen, this would drop to around 15 to 17, depending on location. It rarely dropped below 15. When I tried the new set up, the first thing I noticed was that the regular stutter in window mode was still there, but now on a much longer time cycle - approx every 45 seconds. The second thing was that in window mode the fps stayed hard on 21, as I would expect, better than previously; however, when I went to full screen, they dropped to around 12 or 13 - significantly worse than the old system score.I cannot even begin to understand why this should be so. Could it be I need a new vid. card. Any ideas would be greatly appreciated.Bud