Monitor/Adapter cable problems?

So recently i've had no issues with my monitor or adapter cable, which is what i think and hope is the problem. Everything worked fine, but one day i shut down my PC, and in the morning, tried starting it up. My tower turned on as usual, i could hear the fan running and the lights come on, but my monitor stayed pitch black. I replugged in my monitor coords, then a message came up saying "Digital Power Saving Mode" and then turns black. It's been having this problem ever since and it takes me hours of unplugging and replugging in my coords to somehow work a miracle and my monitor somehow works until i have to turn my PC off again. This is becoming a huge pain and i don't want to spend money on a new monitor unless i know it is the problem. I have already tried hooking it up to my friends monitor and it worked perfectly fine, except one issue. Everytime i try to open a game, it says something about DirectX9.0 not being supported, or my graphics driver not being supported, or failed to find a valid display mode etc. This is also the case with a different adapter cable as well. So i'm wondering if this could be an issue with my tower? Because i've also been having an error with a .dll file error problem that I have posted a seperate thread on. It prevents me from opening certain files like Skype, or my Catalyst Control Center, thus meaning i cannot update my drivers, which i know they are out of date and need to be updated. But could this be the issue, and in order to use a different monitor it needs to update something on my pc, but it isn't able to? I know i may not be explaining things very well, but I don't know much about computers, so any advice or help is appreciated. If you have any questions feel free to ask me and i'll try my best to give u better detail (I know i didn't explain it very well). Thank you

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