Computer&Monitor not displaying properly

[Arnhols]

I need help. I can't get my pc to display on monitor, even though they are both on. My monitor receives a signal from my pc but does not display anything (it says Check Signal Cable) but my Cable is fine (DVI, works on other computers).
My pc was working fine, and then one day I turned it on just to have this happen, and it's been like that since. I cleaned the insides of the pc one day, and it worked for a short while, but when my computer needed to restart, it stopped again.
I don't know the specs for it exactly (Not hardware tech savvy) but I know it is a HP Pavilion and that it has been upgraded a few times (Just the GPU and HDDs though iirc) and it is second-hand, it was given to me by a friend.
If someone tells me where I could find the specs, that'd be great, and I would surely update with them.
Please and Thank you in advance.

 

[ffg7]

what is the numbers & letters after the word "Pavilion"?

 

[Arnhols]

HP Pavilion a6530f PC.

 

[ffg7]

specs link http://support.hp.com/ca-en/product/HP-Pavilion-a6500-Desktop-PC-series/3733085/model/3740334/document/c01463060/
motherboard link http://support.hp.com/ca-en/product/HP-Pavilion-a6500-Desktop-PC-series/3733085/model/3740334/document/c01357135/

 

[Arnhols]

We have the specs now; it'd be nice if someone could post a solution to help. I need this computer to work (I work from home) for my job. I'd like to avoid costly computer repair fees if it's somethin I can just do myself, with some instruction.
Please and Thank you in advance.

 

[ffg7]

do you have or can borrow a power supply to hookup to just the motherboard & maybe the videocard if it needs it but not to the drives to see if the computer posts?