What to do?

ok so i'm new to this forum and i was wondering what i shoudl do?

I have an msi p67a-gd65 and it is after a couple of hours of gameplay making my whole computer lag, what i mean by this is that i can be playing a game or just doing nothing and when say moving the mouse it will move pause move pause and this is the same with gameplay and if there is audio it will make really bad noises, I am convinced it is the mobo because i have tested every other part (evga gtx 570, i5 2500k, hdd, ram) have not checked the psu but from what i have read i dont think it is the psu, also some added things ever since i have had it i have had like beep codes when it turns on and could never figure out what there were after lots of searching and the manual had nothing, and recently the time between when you turn in the pc and the bios loading screen has been extending from like 5 seconds to about 15-20, after all this trouble shooting i have basicaly confirmed that it is the mobo that is the problem and was thinking of taking it back to the store i bought it from and getting a trouble shoot by them for $50 which seams pointless beacuse i kind of already know what is wrong but then they can hopefully send it back get it repairded by msi or a new one, but this could take a long time and considering it is christmas as well, would it just be bette to get a new mobo say an asrock z77 extreme 6 fro $165 and get it now or wait a long period of time? 

please help thanks

Seems like you've isolated the problem, and it very well may be the motherboard. What I would do is ditch the msi, and get an asrock z77 extreme4, as it has a MUCH better value than the extreme6. I think I've seen it for around 100 to 120 on newegg, but you'll have to check.

thanks for that and yes i think i have decided to buy a new mobo, i live in Australia and it is 135 on pc case gear an Australian store compared to 165 for the extreme6, so what are the differences between the two and why is it better value with only the 30 dollar difference? the only difference that i could find between the two is a mini pci express slot i dont know what that would do for you that a regular one cant.