When your arrow turns into a colorful spinning disc, your Mac is hard at work on a processor-intensive task. This is generally normal behavior—your Mac may be rendering or calculating something, or even spinning up the hard drive after being awaken from sleep. Depending on what task is taking place and how many applications you currently have open, you should see your normal arrow return in a few seconds. Sometimes it may take a little longer.

However, if the disc continues to spin and won't go away for several minutes, you can make it stop by doing this:
1 Force Quit the application (or the Finder) that you're stuck in by simultaneously pressing the Command, Option, and Escape (Esc) keys. Please note that you will lose any unsaved changes in the affected application.
2 In the resulting Force Quit window, select the affected application (or the Finder, if that's where the spinning disc occurs).
3 Click Force Quit.

If your Mac constantly displays the spinning disc cursor, try restarting the computer to see if that helps. If not, try repairing your hard disk with Disk Utility as follows:
1 Insert the Software Install disc that came with your computer.
2 When you see its disc icon appear on the Desktop, restart your computer (from the Apple menu, choose Restart), then press and hold down the C key on your keyboard to start up your computer from the disc.
3 Continue holding the C key until your Mac finishes starting up. When you see the Installer screen, choose Open Disk Utility from the Installer menu.
4 Select your computer's hard disk volume from the left pane, then click the First Aid tab.
5 Click Repair Disk. When the repair is finished, restart your Mac from the Apple menu.