How can i get my ram the speed its supposed to be at?

Ok. where to start? I have a PN6 SLI 650i motherboard and a e6600 processor at the stock of 2.4ghz. I used to have in 2gb of 400mhz Ram and that was really slow and dragging down my performance in my games, so i decided to upgrade. I looked into what my motherboard can support and i got the best upgrade i could get: Gskill 4gb 1066mhz ddr2 memory (see link below)

I had some problems getting this to work. first off, when i started up XP it said i had 3gb of memory installed instead of 4gb but cpuz said i had 4gb of memory...but they weren't running at full stock speeds (1066). instead they were running at 800mhz.

i went into the bios and changed it from "linked" to manual and edited the mhz to 1066 and when i rebooted, the screen went black. It took me awhile to figure out how to reset the defaults again. (unplugged power and waited). I don't understand. Everything is good, the mobo supports it, the ram should be working at its full potention but its not and i need help. I don't know much about overclocking, do i have to mess with the CS or something like that? the voltage?

WHY CAN'T COMPUTERS BE EASY!?!

http://www.newegg.com/Product/Prod [...] 6820231166

not sure if this is helpfull but my fsb is at 1066 right now, so can you not have your fsb speed matching the same speed as your RAM speed?

do u have windows 64bit or 32 bit?

Just a minor correction jsc:

The 2 part is not the doubling factor. DDR stands for Double Data Rate. As an example: DDR3 is double as well (not tripled).