Why is my gaming laptop slow?

I have a qosmio toshiba gaming laptop that I bought last month. I play minecraft and tw: rome 2 on it so far and it runs great! But now whenever i play rome 2 the battles lag and it is getting annoying. I never downloaded anything but chrome on the computer, never got a virus (i scanned too to be sure) and never adjusted the game settings to higher. Plus i make sure the computer is updated as well. So why is running bad? How can I fix?

If you're talking about this one http://www.toshiba.com/...agpspn=pla

it should not be lagging if it is that one, but anything else that costed less i'm guessing it could just be an inferior gpu in it. Try running disc defrag and also download ccleaner to clean our your temp files. And a malware scan and virus scan can't hurt anyone also