Mac pro laggy?

My friends brand new macbook pro with snow leopard is kinda laggy. He has had it for about a month.
Sometimes when he in on itunes or safari the spinning wheel will just come up.
For example i was using google maps street view and the wheel just came up for like 12 seconds or so and safari was frozen.
Why would this be happening?
He thought it could have been cause he had the Sims 3 disc in the drive (but it wasn't opened up).
Should he take it back the store?

He can take it to the Apple Store for them to troubleshoot. This seems to be a problem as of late with those that have upgraded to Snow Leopard on certain machines. Apple has yet to release a fix for this. Advice: tell him to backup his system to an external harddrive and then downgrade to Leopard.