Gpu not working after cmos reset

Hi, I recently bought a pc from a friend that gets stuck on the bios splash screen and wouldn't let me use keyboard or mouse to access the bios or anything and took ages to boot to windows. I did a cmos reset by unplugging everything and taking the battery out, This didn't help. I then tried resetting using the clear cmos pins on my motherboard, This started my problem. Now all I get when using my gtx 970 is the bios splash screen and then nothing it just goes to a black screen and nothing else. But if I use a vga cable to an old monitor using the onboard graphics the pc comes straight up with cmos/bios has been reset please choose a default optimisation. I turned legacy mode on to try to get the keyboard working and turned off the splash screen picture. After it restarted it loaded windows and let me log in, I shutdown the pc and plugged my gtx 970 back in. When I turned the pc on the splash screen picture was back and I had no keyboard and mouse again and it went straight to the black screen again after waiting about a minute for the splash screen to go. For some reason whenever I now use my graphics card it seems to reset the cmos or whatever because when I plug back into vga on board it says bios/cmos has been reset everytime. The only way I can get into windows is by taking out my 970 and using onboard vga or dvi. It seems to either not like something or its got massively confused about what's going on after the reset. The pc was working fine apart from getting stuck abit on the bios splash screen and had been working with the gpu plugged in and running games fine no more than 15 minutes before doing the first reset. but now its just this over and over. What do I do??

My specs are:
I5 2500k (stock)
Msi gtx 970 armor 4gb
Patriot blue 8gb ddr3 1333mhz ram
1tb hard drive
Gigabyte ga-h61m-s2pv rev 2.0 mobo
Corsair CX600 psu
Windows 10 64-bit fully updated.