I ran MS Flight Sim 2000 on a PII 350, and had to turn down many of the settings to get it to perform decently. X-Plane is definitely easier on your hardware, and isn't that far behind in scenery detail. If you do want all of the scenery details though you will need a faster computer, but if you're just looking for something to practice procedures, turning down graphics setting s will work fine. X-Plane at the time ran pretty well, but I haven't tried a more recent version of the sim that computer. Most flight sims benefit more from faster processors and RAM than video cards, so if you can you should look at upgrading the processor.
goates