Since the question doesn't specify when the pinwheel icon appears, there could be various reasons. It could be connectivity issues with your modem, installed software is taking awhile to load, your browser's flash media might have quit unexpectedly, depending on how old your MacBook Pro is, your hardware might be having a difficult time keeping up with accessing or loading an application.
It need some time to load
MacBook Pro is the best you can get
macbook pro with retina display way better
The macbook pro!
MacBook Pro!
you probably should get the MacBook. they are cheaper than the MacBook Pro. now, if you want a bigger screen, then get a MacBook Pro.
There is no age limit for getting a MacBook Pro.
MacBook Pro was created on 2006-01-10.
The best place to buy a macbook pro is apple.com.
The MacBook Pro cases are much larger and sturdier the the MacBook Air cases.
The Macbook Pro was upgraded ,as well as the iMac.
Detailed instructions for doing this are here: http://www.ifixit.com/Guide/Mac/MacBook-Pro/SuperDrive/85/6 however this will void your warranty if you are not an apple certified technician.
Macbook air