No signal to monitor after opening the pc case

[NoCyberPls]

So the story goes like this. Yesterday I noticed that people who I bought my computer from had placed one of the RAMs wrong so I opened the case to place it correctly. After opening and placing I put the case back and opened the computer. But after this my monitor just says "No Signal" and goes black. I think my computer works fine, every fan spins and so on. I have checked cables and stuff and they seem fine. I have tried taking RAMs out and running with only one and using different slots for them. I have also tried taking my graphics card out and replacing it but still black screen. I really don't know what to do.

If you need to know more about anything please ask. Right now I'm not at home since I can't use my computer there but if you have questions I try to answer asap.

And I also have question about my graphics card. My current graphics card is sapphire radeon hd 6790. After I took fan out of this I found something grayish substance which would also stick to my fingers if you touch it. Is this what it should look like if you take the fan out or did something perhaps melt there? Also if something melt there, could this be the reason why my monitor says "No Signal" after I turn my computer and monitor on?

 

[clutchc]

The sticky substance in the card sounds like it could be a problem. Or it could just be excess thermal grease from between the GPU and heat sync. But if it is electrically conductive grease, it could be a problem.

What motherboard/CPU do you have? Do you have integrated video you can test with if you take the card out of the system?