No display + No Beeps = Frustrated

make sure that your HDD is listed in the boot sequence. It should be already but you can check in your bios.

I would, but the monitor won't even display anything. You can tell the monitor recognizes that the computer is turning on, but the screen will only turn gray. I've tested the monitor, so I know it is not a faulty monitor.

Go to an absolute min system. Just ram and video no hdd or floppy, or DVD.... - see if you get beeps.
-Bruce

Have you tried different outlets? Maybe try bringing it upstairs to the original outlet and see if that does anything. Worth a shot I suppose.

Check the lights in the back. Look at Diagnostig lights section.

http://support.dell.com/support/edocs/SYSTEMS/dim5150/e...

This. If there is no display its either GPU, RAM or mobo. Considering yours probably is using a IGP, the GMA 950, its probably the mobo or RAM is bad.

When I remove a CD player, I get 2 beeps. Switching outlets does not change anything. I tried to diagnose the system by the lights, but when I turn the computer on, the lights just go crazy. 4 blinks, then 2 and 3 blink, 1 blinks, 1 and 4 are steady and then 2 and 3 blink on, then all lights turn off.

How would I tell if the mobo is bad? And if it was, wouldn't I hear a beep or the monitor not even register the computer turned on? (even if there isn't a display)

Also I just checked the hard drive by putting it as a slave in my main computer and it works fine.

Irpwns, I had a similar issue with my Dell E510. You would never guess what the problem was... It was the Frontal I/O Panel (the component that allows front USB connections, headphone ports, and the power button).

My issue might be a little different than yours. I would press the power button, it will just blink a amber light for 1-2 seconds. The fans will also start for 1 second. Then everything stopped. It looked as though it was the PSU because it looked like the E510 was not getting enough power. But the PSU was perfectly fine, I even tried it after I got a new I/O Panel for my E510. I still kept my older PSU because it cost me 60 bucks and sending it back by paying 20 bucks return shipping was not worth it.  

Unfortunately, Dell E510 is a old model, so you will probably have to buy a used I/O Panel from a third party seller.

http://www.ebay.com/sch/?_kw=dell%20e510%20i%2Fo&_clu=2...

I know it sounds crazy, but you basically tried everything else, right (PSU, RAM, monitor)? I do not think this would hurt to try.

Before you actually got out and buy one, try booting your computer by doing a hard CMOs. I was able to boot my messed up E510 by taking out the Frontal I/O Panel and booting it by doing a Hard CMOs each time.

Here is a link to my problem I had, which I fixed with assistance from Tom's Hardware users:

http://www.tomshardware.com/forum/287750-28-improper-sh...