How do i check what is open on my macbook pro

Question

my computer is slow on start-up and when i move to different windows all i get is a spinning disc

Answer 1

Generally, you can hold the command key + Tab key and you should see the apps that are open (e.g. Excel, Word, Numbers) but you have may have background apps.
Try Removing any start up apps that are running in the background. To do this:
1. Make a  backup
http://support.apple.com/en-us/HT201250
2 Start up in Safe Mode
http://support.apple.com/kb/PH18760?viewlocale=en_US&locale=en_US
Immediately after you hear the startup tone, hold down the Shift key.
Release the Shift key *only* when you see the progress indicator. Do *not* release the Shift key early.
Once in Safe Mode check your System Preferences for incompatible login items
See
http://support.apple.com/kb/PH18759?viewlocale=en_US&locale=en_US
Test your login items
    1    Choose Apple menu > System Preferences, then click Users & Groups.
    2    Click your account name below Current User, then click Login Items.
 Make a *list* of the login items—you’ll need to remember them later.
    3    Select all of the login items, then click Remove .
    4    Choose Apple menu > Restart.
    5    If this solves the problem, open Users & Groups preferences again, add the login items one at a time, and restart your Mac after adding each one. 
When the problem occurs again, follow the steps above to remove only the last login item you added.
*list*
Here is a third party source regarding how to save your startup items.  Has a nice tip on how to save the login items.
http://www.maclife.com/article/howtos/how_remove_startup_items_os_x