Complete pc melt down HELP!!

[jaackla]

Okay well yesterday my pc was playing up it freezes on games a lot and closes so someone said reset cosmos or what ever its called so i did that and my PC WENT **** UP i had to reformat and then it wouldent start up because the boot option changed so it wouldent let me re install windows but i finally got that working and re installed everything but now my pc seems so much slower and not working like normal :S like just now i played league of legends and through out the whole game it was flashing like mad and im overclocked to 4ghz so not evan that bad
my pc specs are:

if someone could tell me why my pc has done a turn for the worst and i brought it march/april 2013

120gb SSD
ARCTIC FREEZER I30
G.SKILL RIPJAWSX 16GB (2X8GB) DD
SEAGATE 7200.12 1TB 6GB/S
SAMSUNG SH-224BB 24X DVDRW OEM
INTEL I5 3570K RETAIL
GIGABYTE GA-Z77X-UD3H MOBO
GIGABYTE AMD RADEON HD 7970

 

[jaackla]

To answer everyone questions
graphics card aint overclocked and ive now put my intel i5 back to normal so nothing is overclocked
ermm i dont no if i reset sata all i did was reset cosmos and then i had to change my boot option so i can re install windows i had to disable sumin so it would reinstall windows on my ssd and i just re formatted my pc and i have all drivers updated and all windows update done too

 

[jaackla]

also i have 60mb connection so its really fast and when i try load youtube vids is take a little while to start but it used to start straight away :S