Running slow and freezing

[Faith and Grace]

Lately my iMac has been taking a lot of time going from window to window. Very slow operation in general. Where you really see it is when I hit Command T. That little colorful wheel comes on for about 10 minutes and the computer is frozen.

 

[6string]

What troubleshooting have you performed.... disk utility, cahes, HD space, etc?
Activity Monitor ... whats going on there?
This is always a good start.
Failing that, either setting up a new admin account and seeing if the problem exists in the new account, or going for a clean install, and preferably a clean install of all the 3rd party software once you know that the clean install is working properly and that all the 3rd party software is supported by the version of OS X you are running.