no video when i start my pc

[geo22]

i built my pc in 2011
when i try to start it i get a black screen

a couple days before i thought it was my pc acting up but it was the monitor
i had tried a different video card. t

this is when i realized it was the monitor
i put my video card back
it prompted me on the start screen for a password
i beleive i put a password in when i built it but i do not rember it

i tried getting into safe mode but i could only get into bios
now when i try to start it the screen is black
i tried the other video card same result

asus m5a99x evo motherboard
xfx radeon hd6850 vid card
amd processor

since i posted this i tried to start it again now there is nothing on the screen it does not even recognize the pc ic connected

 

[scout_03]

did you check the cable from monitor to pc .

 

[geo22]

why bother answering i got a new wire and i have my laptop hooked to it to confirm the cable is working

 

[COLGeek]

This is likely not a display issue since it seems you can see your BIOS upon power up. Is that correct?

When was the last time this system worked properly? What, if anything, have you changed or installed since it worked?

Do you have access to another video card?

 

[geo22]

no when i start up now the lights come on the fans start but nothing on the screen.
when i first put my gpu back it prompted me for a code on the statrt up i could get into my bios
now i am getting nothing. i changed my gpu and still nothing on my screen
it is an old computer it was working properly 2 weeks ago
the sreen on the monitor i was using was breaking up i thought it was the gpu
so i just left the pc sitting.

 

[COLGeek]

As an older system, it could be anything. The most likely culprits are a defective motherboard or power supply, given the age.

Do you have access to another, known working, PSU?

 

[geo22]

As an older system, it could be anything. The most likely culprits are a defective motherboard or power supply, given the age.

Do you have access to another, known working, PSU?

yes. but the computer i am having the problem with is a modular supply
my newer computer is semi modular
so what is your suggestion to check the power supply

 

[COLGeek]

Swap the known working PSU (and all of its cables) into the system you are working on. This will help isolate the problem.