4pin ATX malfunction

[pinaki.ghosh.2346]

My Desktop PC Specs:
1. MoBo (Intel Essential Series - D945GCNL)
2. HDD - 500GB (Toshiba)
3. Graphics Card (Nvidia Zotac 710)
4. RAM (DDR 2) - 2GB 800 MHz(PNY) + 1GB 667 MHz (Transcend).
5. OS - Windows 7 Ultimate (64bit)
6. New PSU - Intex Smart 450 Watt.

Facing Problem/s:
When 4pin ATX plugged in, 3 beeps with no display (CPU fans rotates).
When 4pin ATX plugged out, no beep & PC boots (HDD rotates) but ""NO Display on Monitor""

Please help me.

Regards,
@PG2346

 

[why_wolf]

What you are calling the ATX 4-Pin is the CPU power.
Nothing will work without this, your computer is not booting up without power to the CPU.

Intel Beep Codes. 3 beeps = memory error. Reseat and/or remove one of the sticks and try again.
https://www.intel.com/content/www/us/en/support/articles/000005473/boards-and-kits.html

 

[pinaki.ghosh.2346]

What you are calling the ATX 4-Pin is the CPU power.
Nothing will work without this, your computer is not booting up without power to the CPU.

Intel Beep Codes. 3 beeps = memory error. Reseat and/or remove one of the sticks and try again.
https://www.intel.com/content/www/us/en/support/articles/000005473/boards-and-kits.html

 

[pinaki.ghosh.2346]

Thanks for the link of Intel Beeping, it helped me to acquire detailed knowledge about this issue. Well, i did some tests (Results below) as per your reply, but my predicted outcomes are too different.
I started my PC with below results :
1. Removed and Reseated both RAMS from slots (1 at a time)*
2. Empty RAM slots
3. Removed HDD**, Graphics card**
4. Unplugged all extra power & SATA cables

*Altered RAM slots
**Tested with secondary

My outcome -
A>> When 4pin ATX plugged in (1-4), 3 beeps every 1second with fans rotating with NO Display
B>> When 4pin ATX unplugged (1-4), NO BEEP sound with fans rotating with NO Display.
NB: Didn't do anything with BIOS (Mine with jumper pins) settings.