Thanks for reading guys my problem is as follows, i have 4bg of corsair dominator ram 2x2bg sticks its supposed to run @ 1066mhz but it will only run @ 800mhz the ram is in the compatibility list for my MoBo and if i set the ram manually to 1066mhz the pc wont post also in the advanced options the timmings are 5-5-5-18 stock but they should be 5-5-5-15 but if i change this it still wont post.
Processor: Phenom II 940 black edition @ 3ghz
PSU: Corsair TX650W
Memory: 2x2gb Corsair Dominator DDR2
MoBo: DFI Lanparty 790FXB M2RSH
GPU: HIS HD4890 turbo
Are you running at the @2.1 voltage recommended by Corsair? Default voltage for most MoBo's using DDR2 is 1.8v.
If it's at 1.8v try raising it to 2.0v and see if it will boot, as you may not need to run as high as 2.1v if you are not overclocking.
Have tried raising or lowering the Processor-NB Frequency Multiplier? If you do this make sure that the CPU-NB HT Link Speed is matched up. It can not be set higher than the multiplier (ie... 10x 200 FBS=@2000MHz~set the link speed to @2.0GHz)
If your memory is 1066, and it will not run at that speed, your MB front bus must be listed at 800 maximum? You should not have to adjust anything if the MB can handle 1066 - What is the OS being used? I might be missing something here in information. Keep Charging!