|Actually, it's PC2-4300. The "2" means it's DDR2. The 4300 is the bandwidth the RAM is capable of when run at it's default speed, however, it's a "rounded" number. If you divide by 8, you'll get the effective speed of the RAM. Divide that number by 2 & you'll get the RAM frequency (actual speed).|
In other words, 4300 / 8 = 537.5. Divide by 2 & you get 268.75.
That means you have DDR2-533 which runs at 266MHz.