Reformatted my pc; graphics are now hiccuping

I play World of Warcraft, I recently reformatted my hard drive. I played WoW with the game-recommended graphics settings prior to reformatting and never had problems, but now I get split-second-long freezes every 1-5 seconds in the graphics, otherwise they are smooth.

I updated the drivers for my video card and installed all my windows 7 updates.

I set all my graphic options to lowest settings to see if that would fix the problem; it did not.

this is my system info if its of any use

CPU INTEL|CORE I7 860 2.8G R

FLASH 8G|TRANS TS8GSDHC6- S5W R

HD 500G|SAMSUNG HD502HJ % - OEM

VGA GIGABYTE GV-R485MC-1GI HD4850

PSU ANTEC|TP-750 750W RT

CASE CM|RC-932-KKN1-GP BK RT

ASUS|P7P55D PRO P55 RT

MEM 2Gx2|GSKILL F3-12800CL7D-4GBRH DVD BURNER LITE-ON

WIN HOME PREM 7 64-BIT ENG 1PK DSP


Regardless of low or high graphics settings, performance is smooth excepting these split-second "hiccups" in the graphics that occur at least one or twice every 5 seconds or so.