Computer runs unstable, freezes after overclocking CPU and setting RAM to 2133 ? Please help

[TD-12]

Hello all. I really need help with my computer. Ever since I started overclocking my Intel I5 2500k to 4Ghz=4.2Ghz my system would randomly or constantly freeze. Also when that happens sometimes I'll get lines or other artifacts on my screen. To start computer normally I have to reset my CPU settings back to 3.2Ghz and memory to 1333mhz. Updating my bios to latest version didn't help at all. Somewhere on this forum, I heard that you need to set CPU and RAM voltage manually but I have no idea what voltage I need to set to overclock CPU to 4.2GHZ. Any tips suggestions would be greatly appreciated.
FULL COMPUTER SPECS
CPU: Intel core I5 2500k (max CPU temperature under full load is 60c)
CPU cooler: Cooler Master Hyper 212 EVO (two fans)
GPU: GIGABYTE GV-R929OC-4GD Radeon R9 290 4GB
RAM: G.SKILL Ripjaws X Series 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 2133
Motherboard: gigabyte ga-z68ma-d2h-b3
Power supply: 800w xtreme gear. Model NO: ATX-CB800W
1x 128gb SSD
1x 1tb HDD for file storage

 

[geofelt]

To oc your 2500K, test with occt.
Gradually, raise the multiplier. Leave voltages on auto.
Leave ram at stock. 2133 makes little difference in real app performance. Think 1-3%.
Run the test long enough until the temperature rise has stabilized.
OCCT will stop if temps reach 85c. TJMAX is about 100c.

Your psu may not be the best quality and could be part of the problem.
Do some google research on it.

Similarly, do some research and google "R9-290 artifacts" You may find kindred folks.