Aspire 8920 problem

Hi there all, I may come across at points as a noob which tbh is the case.

I have a Aspire 8920 and I run World of Warcraft and I had terrible problems with low fps, when I checked my cpu monitor thing in windows side bar when the low fps happens I see that its maxed at 100% so I had sent my machine back to Acer to be repaired and they have aparently replaced the graphix card.

I have the machine back now and Im still having major issues trying to run WoW, the only way I get a steadyish frame rate is if I have to have all settings down to min which obviously makes the game play a little naff. With any increase in setting raiding is an inpossibility, its just unplayable.

Is this machine of capable spec to be able to run it effienciently or should I get a big hammer and smash it to bits? or is there more of a underlying problem that acer may not of picked up on at the time? or is there something that I can do to enhance it performance.

My partner also plays SIMS3 and even with that installed on here its really jumpy.

Any help in this matter would be greatly appriciated and feel free to ask me anything to help you in err helping me

Many Thanks