At 39FPS you should not notice anything as the human eye cannot detect anything above 26 FPS, so defrag and turn off that Shift-Z
I have to chip in here, thats such a common misconception that I'd it's almost attained the status of an urban legend. The human eye can distinguish differences in the number of frames per second well beyond 60 fps, some studies suggest even beyond 200 fps. I don't have any articles to hand unfortunately as I'm about to head out but if you do a bit of googling I'm sure you'll turf up plenty of research to the contrary and very little that actually states we can't detect anything above 24/25/30 fps. I do however agree that turning off SHIFT+Z so you can't see the fps will improve things dramatically. It's probably the most important piece of advice in gaming; play the game, not the fps numbers.
To get back on topic; the first thing I'd be looking at is your mouse drivers. Do you run your mouse with one of those bloated pieces of software that sits in your system tray quietly nibbling on your system resources? Unfortunately these can sometimes cause problems, I'd recommend getting rid of anything that sits resident in your systems memory and sticking to a bog standard windows drivers for your mouse and keyboard, even if it means loosing some of the functionality of those buttons manufacturers seem obsessed with sticking all over peripherals these days. I recall having stuttering and fps loss like this years ago and it took me a long time to track down the cause... it turned out my Logitech mouse (and associated system tray program) didn't like it when my MS Sidewinder was plugged in and caused a huge drop in fps every time I moved the mouse. I simply picked up a USB - PS/2 converter and plugged my mouse into the good old PS/2 port and installed a standard windows driver and haven't had issues since.
In my experience you certainly shouldn't have to defrag after installing one aircraft, if you'd just installed FS Global then sure, but not one aircraft. I actually think that if you defrag every time you install an aircraft that you're causing undue wear and tear on your hard drive to be completely honest. Incidentally the default Windows defragger is a load of old cobblers, I'd spend a little and pick up Ultimate Defrag from Disktrix (
http://www.disktrix.com/). Be warned though, a full thorough defrag can take up to 24 hours if you select certain options, but it is well worth doing. It will move all of the data you select (in my case C:\Windows and C:\Games) to the outside of the hard drive platter, and then stack everything else up against it leaving the inner part of the disk empty. This cuts down on disk seek time and if you've got a poorly fragmented drive you will notice a difference. Chances are your hard drive may last a bit longer as well as it won't be thrashing around all of the time. Run that once a month (I tend to recommend doing it as part of a cleanup schedule including an on-line virus scan, a system/registry clean and a quick run through with adaware and spybot).
