Can you tell us at what point the cursor is spinning?
Is it during the boot or when you are using a program?
Let us know
Just remember never to show fear as they can sense it.
Can you force quit the program by pressing apple+option+esc then selecting the program from the list and quitting, (If it wont for ce quit and the machine is locked up could you pres nd hold the power button till it shuts down.)
Once you have done that shut down your Mac and wait a moment then power it back up, As soon as you let go of th power button press and hold down the SHIFT key till you see the load icon appear under the Apple logo then let go and wait up to 20mins for your machine to Safe Boot.
Once the machine has safe booted could you just restart like normal and then relaunch your program and let us know if it behaves itself.
What program is giving you the issue?
Also do you know how much free disk space you have?