I need help! PC went to black screen after changing priority of rpcs3.exe process

Hi everyone this sucks I need help my PC is unusable, I can't turn it off and no mouse shows, so I was testing Skate 3 on my Windows 7 Ultimate 64 bit, and suddenly after changing the process priority to "above normal", my PC started to run slow and went into Black Screen with the GPU running at full, I can't turn it off or restart unless I turn off the PSU, I tried using no GPU but it wouldnt work just a black screen no mouse, then I put it back on and also removed the Mobo battery but still no luck, it did boot after 2 tries of turning off and on the PSU and I tried repairing the system startup but in the process of repairing it went into the black screen and no signal on my monitor, I then restarted again by doing the same thing and then tried to launch normally, and it did, but after a while it just randomly goes to the same damn black screen and I cant do anything as I said, please help this sucks so much and I need my PC to work because I'm at a home office job, I removed the program and Skate 3, but it still happens, please please help me, sorry for my English, I'm not a native speaker. These are my specs if theyre of any help:

Windows 7 Ultimate 64 Bit PSU: EX2 Extreme 525 Cooler master 8gb Ram DDR3 one HyperX one Adata 4gb each GPU: R7 260x XFX CPU: AMD X4 845 Mobo: Gigabyte f2a68hm-h HDD: 500gb Hitachi

I also have the GPU drivers up to date.
Please help me, thanks