having issue with my computer

[ferengi4]

So I have had my computer for less then a year and recently its been randomly rebooting itself on its own. Either while gaming or just watching a video on the internet. I thought this was a PSU issue and bough a new PSU and installed it but it still reboots randomly. Any ideas?

radeon 7770 video card: http://www.newegg.com/Product/Product.aspx?Item=N82E16814150598

8 Gb Ram

700 watt modular psu http://www.newegg.com/Product/Product.aspx?Item=N82E16817190031

asus motherboard

amd-8120FX http://www.newegg.com/Product/Product.aspx?Item=N82E16819103961

 

[tiny voices]

Possibly RAM issue. Run MEMTEST.

Possible CPU overheating issue. What are your temps? If you heatsink installed properly?

 

[ferengi4]

Possibly RAM issue. Run MEMTEST.

Possible CPU overheating issue. What are your temps? If you heatsink installed properly?

I get 40C when doing nothing and about 60-70 while gaming, the heatsink is installed properly I believe since I cant wiggle it or make it move at all when its on.

Also I put memtest on my usb and then rebooted my pc, a trinity thing comes up and asks to select the boot device and only lets me pick my cd/dvd drive but still wont boot. What should I do? do I need to make a boot cd or something?