I'm having problem overclocking my pc. Here's my pc spec.
PC spec
Pentium 4 3.0E
MSI 865PE Neo2
Corsair TwinX XMS 4000PT 512MB (500mhz) 3.4.4.8

I've tried overclocking my RAM's clockspeed to 500mhz (currently running 400mhz) but it couldn't boot. I tried running at 433mhz, it works fine but i wonder y i can't overclock it to 500mhz. The other day i asked a guy in the shop. i told him to test on my RAM. he showed me how he did it. yes indeed he really could overclock it to 500mhz with the same set of mobo n processor as mine. I've tried configured everthing in the BIOS setup but it still doesn't work. wonder wats wrong with it.
Can any1 help me out? Pls gimme some guidance. Maybe i did something wrong overclocking it.
Thx ^^

Sorry i'm kinda noob ^^ wats a vdimm? i'm sure my processor can stand 250fsb.