8200 dell dimension - beep noise

Yes I have a computer I am looking at for a customer of mine, and its a 8200 Dell Dimension pc. Default specs from Dell.

2.4-GHz Pentium 4 CPU, 256MB of RDRAM, Windows XP Professional, 80GB hard drive, 24X/10X/40X CD-RW drive, GeForce3 Ti 200 graphics card with 64MB of DDR SDRAM, 17-inch Dell 1702FP LCD monitor, SoundBlaster Live Value sound card, Harman Kardon HK-395 speakers, network adapter, modem

The problem is when I boot up the pc, I get a long beeping sound from the pc (about 6sec before the beep goes away). I thought it might be memory but when I do a process of elimination.... nothing, the beep still exits. So I unplug the connector for the P4 (the small connector attached to the power supply. Beep goes away. So i am thinking its the mobo, so i tried mine that had the same P4 connector, and the beep came back. If i unconnect the P4 connector the beep goes away. If I reconnect the beep comes back. No video or nothing on the screen with the connector hooked up or not.

Sounds like the motherboard? I thought it was the cpu but I read somewhere the connector for the P4 is really not needed.

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Any ideas?

8200 Diagnostic Codes:
http://support.dell.com/support/ed [...] tm#1101734

Other 8200 Documentation:
http://support.dell.com/support/edocs/systems/dim8200/

Ok I have tried another PSU and still the same problem. Thanks for the Diag. codes. The diag leds that were on Dell site unfortunately didnt match up with the diag. code i hade. I had to called Dell and ask them what diag code i was getting. We troubleshooted it down to the memory. That P4 connector not hooked up really through me off cause, i didn't know sometimes it didn't even power up the system if not connected. PSU going but nothing from the board.

Thanks for all your help.