Once upon a time, there was a bright young flight simmer who over the years graduated his way from FS3 (on one floppy disk) through FS4 to FS95 ... and so it went.
One day, having been amazed that his computer would run FS9 pretty well, he saw that a new sim, FSX was about to be launched. In wonderment, this bright young flight simmer downloaded the demo, and because his computer was only XP SP1, he couldn't load it or run it. So, he loaded it onto his kids' computer which was although lower than the spec of his machine (but not by all that much) was XP SP2.
Imagine his amazement then when FSX ran at 20fps on this humble 1.7gHz, 256mB RAM, GeForce 2 machine! At minimum settings though. Lo, he upped the settings to medium and the machine sighed and dropped to 4-5fps. Lo, he upped it even further and the machine verily started to creak in frustration until finally, a warning message of low virtual memory appeared, rapidly followed by an 'out of memory' message, and a loud raspberry from the poor old AMD Sempron as it respectfully requested me to reboot the computer.
So, our young flight simmer knight, having thought deeply for a few milliseconds about the intricacies of upgrading his own machine to SP2 and wondering whether it would be worth it all since his 2.0gHz, 1gB RAM, Radeon 9200SE rig probably wouldn't fare much better, thought 'sod it' and uninstalled the FSX demo from the kids' computer and decided to face simming life with his old faithful ...
...FSIX!!!
And he lived happily ever after - or at least until he could persuade his dear wife that a 4gHz 2gB RAM machine would be a worthwhile investment for a SILLY COMPUTER GAME (not my description).
Oh well.