I have bought 2 new win power power supplies over the past week 1 550w and 1 800w I found that the 550w was no where near powerful enough for my system and would not boot past the BIOS the 800w arived today I fitted it and same issue, I then lowered the CPU multiplyer in the BIOS to its lowest setting and what do you know it worked and booted to windows. However I tryied to run Sysoft sandra to check the benchmarks and it just restarted any ideas. I think that these cheap win power PSU's are the root cause.

Post the brand and models of the PSUs and your system.

The PSU make is Win Power 800w AMD Phenom Quad Core 2.2ghz Gigabyte Motherboard GA-MA770-DS3 Nvidia 8800 GTS DDR3 640MB 4x 1GB Geil 800mhz DDR2 RAM 2x 250GB Western Digital Caviar (RAID 0) 2x DVD rewriters

If the link below is for your PSU then the specs don't look too bad. On modern systems the +12 volt rails are the most important. The specs say 18A & 21A. The problem is the total amounts add up to more than 800W. The manufacturer may be fudging the numbers. I am in the USA so I don't know what brands are available in the UK. You could have incompatible RAM or the RAM settings may be set wrong if using default settings. Your RAM, for instance probably is supposed to run at a higher than jedec specs of 1.8v Off hand I don't know what your CPU draws but I would guess the video card would be about 10A by itself. http://www.watercoolinguk.co.uk/cat... http://en.wikipedia.org/wiki/DDR2_S...