Problem when i turn on my pc it never turn on but the red light is still blinking like it was loading and no beep then my monitor was blank...but sometimes it run what could be the main problem of my pc?pls help me tnx!!!but the fan still running and

Hi jake, that red light blinking is your hard drive. It's running.
Let's address 1 power connector. Still have your manual?
Go to pg. 11. (Make sure your power cable is unpluged), re-move & re-connect the ATX_ 12V Power Connector.
Next remove your AGP card. Using a strong flash light to help you see. Clean out the AGP's slot on the mother board. (canned air works well. Check the copper connectors in the AGP slot. Sometimes they get bent. Gather a cotton swab & a bottle of house hold alcohol & lightly dampen the cotton swab. Clean the AGP card's copper contacts. Do the same to the copper in the AGP slot. Firmely & evenly re-seat the AGP card. Plug in the power cord & boot the PC. Still no display? Re-check the cable & connector from the PC to the monitor. ( nice & snug).
Double check all data connectors & power connections to each device. Next if you have more than one dimm in a slot remove one dimm. Try starting PC. (did you get display)? Swap the dimm with the other stick. Start the PC.
Last item on the list. Clear your cmos (reset). Pg. 9 in your manual. Move JP1 (that is currently connected to pin's 1&2. Move to pin's 2&3. (wait about ten seconds). Replace JP1 back to pin's 1&2.
Re--start the PC & try entering the bios. Press the Delet key every 2 seconds till the bios main menue loads. Re-setup your settings, starting with the time & date.
Try all of the above first. If everyting has failed to allow the PC to boot than I'll post a web site that will test your memory. You will be able to make a bootable floppy disk that will test you current memory. This link is listed below:
http://www.memtest.org/
Scroll down to ** Memtest86+ V2.01 (21/02/2008) **
Typrd all in red.
Download: Download - Pre-Compiled package for Floppy (DOS - Win) file.
This will test your memory.
Good luck & thanks for using FixYa

I welcome any more question regarding this issue.
please vote

There are many things that can cause this, first obvious causes would be bad ram, dead mainboard or hard drive.. i say dead motherboard due to the fact you say there is no post beep on startup, easy way to tell, remove all the ram, and turn it on, if it squeels at you, you know the motherboard still at least is somewhat operational, next thing try replacing the ram.