M17x R4 Problems - Gpu Issues

So I've got an Alienware m17x r4 with a 7970m gpu in it. I have overclocked the gpu to 900/1500 from the stock clocks of 850/1200. I don't really know much about it but I've made sure that these are stable and the temperatures are good so I've had it oc'd for a couple monthes now. Just recently I wanted to downclock it back to stock clocks, so i clicked reset in afterburner and it appeared to be okay. However after resettting stock clocks I was getting low fps. The reason I was alarmed was that I was barely getting 30fps on league of legends when I had reset my clocks for my gpu. I tried again, and this time decided maybe reinstalling LoL would help. During the time I had decided to watch a video. As I tried to watch it the entire screen was covered with multiple colors and horizontal and vertical lines. I managed to exit out of the window and it stopped. I'm mostly wondering, why did this happen? Is it bad?

Also, on another note my computer has been shutting down randomly and I thought it was overheating so I re enabled core clocking and it continued to happen. So after some different things I noticed that my computer was failing the "advanced pattern test" in the alienautopsy program. After some different things I had ended up using the dell diagnostics and it appeared to fix the problem however I have to see if my computer will be shutting down randomly anymore. Do I need to worry about this anymore?


Thank you for all who reply. I am quite frustrated and worried that I have done something that caused some hardware damage. Any insight would be helpful!

 

Overclocking is never good for the VC, it might have gotten damaged because of that but hopefully the problem fixed itself as you state.