Change in the Power Supply, and now No Display

Hi, I am running a P4 2.53 GHz processor on a ASUS P4PE motherboard, I have 512 of Corsair XMS DDR, and my video card is a POWERED by ATI, 9000 Pro. Everthing was working fine until i recently decided to upgrade my powersupply from 300 Watts to 400 Watts, with a WORKING power supply a friend had given me. It is a generic brand, and everything seems to be getting power. That ATI card has a little fan that spins fine, so I am assuming it is getting power, and yet my monitor just blinks the little green light with no display. I do know that it is connected, because when it is not connected my monitor has a little error message. My monitor is a Samsung 955DF. I have tried the old powersupply to no avail,  and various other monitors,  i have re seated the card twice and rebooted to many times. Any help would be appreciated.
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Chances are you knocked something else loose. So get back inside of the machine and reseat everything including all the power connections to every device. I am thinking the harddrive connections probably came loose.

The Crazy One
That or you shorted something out and now its not putting out a proper signal.
You can have a power supply, a motherboard, and a video card all sitting on a table connected, and plug your monitor in and you should still see the bootup ascii text.

Point is, you dont need to have a hard drive, keyboard, mouse, printer, cdrom, fans, or anything else plugged in. so worrying about a bad connection elsewhere is irrelevant.
Plug your hd's ide into your cd rom, leave 1 unplugged, etc.. youll still see it boot up, show the bios manufacturer and then see the error message..

I'd suggest plugging the monitor into onboard video if u have it.. or picking up a cheap old old agp card. to test vid..

another idea, if its blinking.. that meens its in sleep mode, so perhaps you have a faulty on/off switch, or jarred something relating to it

try hard starting the pc (check w/ your mb's book on how to jump-start it) most of the time, its just slipping a jumper on 2 pins..

good luck bro
If you are sure all your connections are fine then it is probably the 400w supply.

Although the overall wattage is higher than your existing supply, it doesnt mean that the psu is better.
More important than overall wattage is the quality of the supply and the amperage it can supply on the various voltage lines. A top quality 300w supply will be far better than a low quality 400w in this respect.

For a rule of thumb I always assess the weight of a psu - it should be the weight of a heavy hotel ashtray or more!

This is a crude measure and is no substitute for reading the label on the psu which should give you the various amperage outputs at the 3.3v, 5v and 12v lines. In addition some psu have combined ratings for 12v and 5v lines - inherently less desirable than seperate circuits and ratings.

Hope this helps
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>>>so worrying about a bad connection elsewhere is irrelevant.

I beg to differ. I have had the same exact problem and it was loose connections that was the cause. :>)
Check the power connection into the board is correct. Check that connections onto the motherboard for power and reset are correct. Ignore the connections hard drive led etc.
Best thing to do is strip down the machine to be bare essentials. Leave the ram,processor,video card in the motherboard and boot and check for post. If it gives beeps then write down the pattern. If you get a post then replace each component one at a time until you come across the fauly component. If this still doesn't work it might be the ram, video card or processor.
I would put my money on the fact that your video card is shot , had the same problem. Just because the fan on it spins doens't mean it's working properly and you will not get the usual "beeps" either.

put in a cheap PCI video card and see if it works.

crazyone a bad connection mustve been shorting out your PS then, because you dont need to have peripherals to see the bios..

And mcadecs right, because the 3v fan is spinning, doesnt meen its putting out proper signal ;)

its getting power yes, but either not enough, or its not doing anything productive w/ it

No short that I know of just reseated everything and it solved the poblem.
Still unsure if you are getting any beeps or not?
Do not fool around.  Get a brand new name brand power supply and install it.  After having your situation happen to me SEVERAL times, it has always been the piece of s**t power supply that comes with most cheap cases.  
Krazzy120Author Commented:
Thanks for all the help guys. However, I managed to solve the problem very simply. I removed teh watch battery from the motherboard and let the BIOS reset, and it worked fine. I'm guessing i just bugged it up by changing the power supply. Thanks a lot though, i do appreciate the input.
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