Power surge please help

[skip1025]

Monday 6:02 a.m. - Had a power surge and pc "clicked" and turned off. I turned back on @ 4:00 p.m. and ...... no sound and (i play WoW) really laggy game play. I took it to Best Buy where i have a friend who works there and he ran a 40 hour "diagnostic" on it and said everything was OK. I bought a new Sound card and brought it home.....reinstalled only to find that it still lagged while playing. I am currently running XP, Radeon X1300 GFX, 4X 512 DDR Ram(2G total), AMD 64 3500+ 2.3 GHz, Compaq SR1834NX is model number of PC. Current syptoms are - running my game laggy as **** were as b4 it never lagged @ all. it loads windows just a lil slower on start up and i dunno what to replace/check/burn =). I personally believe its my HD but i dunno its not noisier than usual but i dunno.....thats why im here. ANY opinions/comments would be appreciated THANK YOU