I put a new power supply in, still get nothing but green light in back any ideas?

So basically you cannot get the pc to POST. Meaning you have just a black screen when you power on the pc, right?

First off, did you attempt to update BIOS before this happened. 90% of the time this is caused by a corrupt bios.

If you are the victim of a bad BIOS flash, don't freak there are some options. First off, if the computer (or motherboard) is still under warranty the Computer (or motherboard) can be sent to the Vendor for a BIOS reprogramming.
If you are a DIY PC builder and the warranty is expired you can take out the bios chip and sent it someone who reprograms BIOS chips or you can buy a brand new chip form them. I will show you my people.

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or

http://stores.shop.ebay.com/Bios-Depot__W0QQ_armrsZ1

For non-BIOS issues:

If you did not try to update BIOS before the problem started then try these troubleshooting steps.

1. Full power down. Unplug the power cord from the Power supply. Then hold down the pc power button (this discharges any residual power in the capacitors).

2. Open the case and reseat the graphics card, hard drive, and RAM.

3. Take out one of the RAM sticks if there is 2 or more. Swap the RAM sticks in different RAM slots. Try one stick at a time to see if you can get the PC to boot. If this works, then the remaining ram sticks are damaged.

4. Set the Cmos jumper to clear. Power up the pc. Power down the PC. Set the Cmos jumper back to normal position, power up the PC.

5. Unplug and replug all the power supply cables.

6. Check the powersupply function. Either by a powersupply voltage checker (20-25 dollars at local PC shop), get the supply tested at a PC shop (usually a free service), put the powersupply in a different pc, or try a different powersupply in the problem computer.

If the Powersupply checks out ok, then you will have to do a process of elimination to find out what part or parts are the culprit of the No-Boot.

Start by pulling all the ram sticks if you have not already. This is the easiest components to check and usually a culprit.

Take out one of the RAM sticks if there is 2 or more. Swap the RAM sticks in different RAM slots. Try one stick at a time to see if you can get the PC to boot. If this works, then the remaining ram sticks are damaged.

If it is not the RAM, you have to continue removing items such as sound cards, un-plugging hard drives and optical drives, other PCI cards. Do this one at a time until you find the culprit. If a POST screen, meaning you can see Anything from the PC brand name to Motherboard brand name appearing on the screen.