ok well i'll start by giving the type of computer i am messing with it is an HP pavilion A705W and heres the problem....a couple of days ago my girlfriends family came to me with a computer problem it turns out that her sister was rough handling the computer while it was plugged in and completly ruined the power supply the input on it was broken and knocked loose and they said when they turn it on it starts up the fans run for a second and then it cuts off....so i brought it home with me switched out the power supply with an equal 250w Bestec power supply....i booted the computer up fine numerous times with no problems at all. Well they bring it home and plug it in only to run into the same problem it starts up the fans run and then it cuts off numerous times before i unplug it. Now i am a little knowledgeable on computers ive built many of my own and i have never run into this problem. I have even gone as far as unplugging the chasis fan the hard drive as well as the disc drive and any media ports on the front of the computer to see if wattage was the case and as far as im concerned it isnt. Now the funny thing is the fans do seem to run a little weaker here than they do at my house. Now it is a 24 Pin mother board and i was messing around with it and when i bring it down to just 20 Pin it runs about like it did at my house the fans dont seem to be running weak at all but it still wont boot up it just keeps running in a cycle it starts up runs for a couple seconds and dies with no screen at all. Yes ive unplugged everything before putting in the new PS....i mean ive even went as far as putting in a new CPU any suggestions? I knew i hated HP for a reason as well as any OEM computers and this is why i build my own.