Well, it seems that that PC is not POSTING. So here you go.
Are there any BIOS Beep Codes? - They are also on that list.
Here is a link to the Dimension 4600 LED Light Diagnostic's
The LEDs on on the back near the I/O plate. There should be (4) of them. Plug in the PSU and press the power button. Then look at the 4 sets of lights. Passed Post will be 4 solid green lights. Find out what light patterns you see and compare them to this chart.
Just my prediction;
I bet you'll find that you'll see (2) Green Lights followed by (2) Yellow.
This is the Code for a memory issue. Either the memory is shot, or the memory slot or memory bus is shot. You'd still get power to the mobo, but it will not post and no fans will move. If you have more then 1 memory module & dimm slots, try only using one module, and move it around to different Dimm slots if you have 2 or 4. Keep tyring to boot.