The only thing "wrong" with PC2100 RAM is that it can seriously limit your ability to OC your CPU, which appears to be happening in this case. At 2.2GHz you're only running a 137MHz FSB which is a mere 4MHz over PC2100 stock speeds. While its possible that 2.2 is simply all your CPU is capable of, its almost certain that your RAM is holding you back (especially if you have a recent pack date on that CPU). You find out what the limit on your RAM is by setting the mem ratio to either 3:4 or 4:5 and see where the RAM craps out. If it still craps out at around DDR274 (137x2), then its your RAM. If you had your heart set on hitting a higher speed, then it may be worth selling your RAM and buying some good quality PC2700 or higher (like Corsair XMS) and see how much higher you can go. If you're fairly happy with 2.2 or don't want to go through the trouble of upgrading your RAM, you might try upping the voltage on your RAM or CPU.