Overclocking Trouble

I have a ASUS A7V266-E mobo, an AMD Athlon XP Palomino Core 2100 chip and 512 megs of pc2100 ddr mem . When I go in the BIOS of my comp and look at the multiplier its not just one number, it's 5.0x/14.0x and the bus is at 100/33 or 133 (at default setting). When I changed to the manual setting to change the multiplier and bus speed the multiplier had other single number options. I changed it to 12x and left the bus at 133. I wanted to just speed my comp up a little to 1.6 ghz from 1.4 to get some more power for games. I thought 133 times 12x equals 1596mhz. I exited BIOS with the exit and save changes option and the comp went to restart, nothing. To try and understand the two number multiplier setting more I tried not using the manual setting but a preset one that was already there, 867/1800 for the CPU speed, same for multiplier 5.0x/14.0x and it boosted up the bus speed to 133/33 or 166. I wasn't to worried about temp because I have a koolance water cooled system, I originally left it at the 1.4ghz setting because I'm paranoid about my CPU temp even thought the water cooling depending on ambient temp keeps is many many degrees below normal with reg. heatsink and fan. Anyway, perhaps someone could shed some light on the weird two number multiplier deal(5.0x/14.0x), does it have something to do with me having ddr mem, if so why is there single number multiplier options.