You should give us a little more information, like what hardware you have, what changes you might have done, and what OS you are running.

You say this happened before a few times?  If so, some part may have failed, after giving you warning that it was on the way out.  Now you have to isolate what it was, so hopefully, you have some spare parts to aid in this.

Some of the things that could be causing your system not to boot up (blank video screen):
- bad connections
- faulty or inadequate power supply
- bad RAM
- faulty video card
- bad cpu
- bad motherboard

You say that you changed the power supply, but perhaps the new unit is not powerful enough.  I recommend stripping down the pc to the bare essentials: one stick of RAM, the cpu, and the video card, and reset the BIOS.  Do not include hard disks, other PCI cards, or other peripherals.

You said CPU hasn't burnt.  Did you actually test it in a different system?  If striping the system down to the bare bones as suggested by Calandor,  you may want to pull the MB out of the case and see if it will run or not. (with video, ram, cpu) Could be the board is shorting out on the case.

hi  Callandor,

The PC specs...
P3 800MHz
256 RAM 133 MHz
MB Legend QDI
Generic TNT32 agp video card
Maxtor HD 20Go
Generic soundBlaster 16
Ethernet card

I stripped down the pc to the bare essentials.. same things... The screen is blank...
I pulled out all PCI cards and AGP card... i pulled the plugs of CD-Rom, HD and Floppy...
I replace the AGP video card for a PCI video card...
I replace the old Power supply for a 250W...
I replace the MB battery
But i remember some scrappy stuff on some condensators...
I'll try to check all peripherals individually.. and i'll pull the MB out of the case...

I'll give you feedback very soon...
Thks for all
Mart.

> some scrappy stuff on some condensators

If you have discoloration or rounded tops on your capacitors (also known as condensators), that is probably the source of your problem.  If these are on your motherboard, then you have to replace the motherboard.  If you are handy with a soldering iron, you might be able to replace the discrete components, but most people replace the board.

Hi Experts,

i put the cpu 800MHz in an other computer (PC#2)... and all i have is a lot of bip (continuously)...
It's stop when i turn off the pc.
The worst thing is if i put back the original cpu in the PC#2... i got 3 bip... and a continuous bip!

i hope i don't make a bad thing!
anyway!
i continue...
Thks for any help
Mart.

If you tested the CPU in a different system, you may have to re-set the bios in the system #2 to detect the CPU properly.  I can't imagine a CPU would cause the other system to stop working.  My guess would be re-set the BIOS.

How can i reset the bios?

To re-set the bios, there should be a jumper near your MB battery.  It is usually marked something like CLEAR / NORMAL.  If you can find it, set the jumper to clear, then back again.  The other option would be to pull the battery out, and let the PC sit for approx 20 minutes. (unplugging the computer is always a good idea)

Hi,

i pulled the battery out (of the PC#2)... i wait for 30 minutes... i got 3 bip... a break... and continuous bip... it's stop when i turn off the pc!!

what could be the problem(of the PC#2)?? the MB is a Asus CUV4X with P3 733MHz and 3X128Mo

Thks again!..

Mart.

hmmm!
Callandor, i don't know the english expression for this... it's like beige-brown stuff on the top of the capacitors (3 of them are affected)... I know this kind of problem can cause a lower performance of the pc...

eccs19 , i've already tested all you said (for PC#2)... and it still not working!

so! i continue to make tests.... any suggestion will be appreciate....
bigs thks for your efforts
Mart.

>I know this kind of problem can cause a lower performance of the pc

It's not just lower performance, but disabling your pc completely!
http://www.badcaps.net/ident/

If your capacitors look anything like these, you have identified the problem.

Hi aleksandrzingorenko,
i'll check the graphic card... i'll give you feedback...

for the PC#1... i posted a topic in the forum of the MotherBoard builder (Legend QDI)... and i'm waiting for an answer...

Thanks again for you efforts.

Mart.

If not response from originator, then I think points should be divided up.

No comment has been added to this question in more than 21 days, so it is now classified as abandoned..
I will leave the following recommendation for this question in the Cleanup topic area:
split between callandor and eccs19 and aleksandrzingorenko

Any objections should be posted here in the next 4 days. After that time, the question will be closed.

Compfixer101
EE Cleanup Volunteer