Mouse clicking not working on Disk Utility screen. How do I select erase button? When I returned home a couple days ago, I had a notification that some updates had been installed. This had rendered my 27" iMac basically useless. It lags horrendously with almost a never ending spinning beach ball cursor. 

I'm trying to delete the HDD contents and reinstall the os, but when I boot to Recovery Mode to get to the Utilities screen, the mouse pointer will move but it will not click. I was able to figure out how to use the keyboard to get to the Disk Utility section but I cannot find out how highlight the erase button using the keyboard. If someone can come up with an answer or easier method, I'd be forever in your debt.
If I understand your question correctly, you want to select a drive and erase it. However, while you've worked out how to select the drive using the keyboard, you're not able to select the Erase button.

In your situation you can do this with by using the ShiftCommandE keyboard shortcut.

Hope this helps. If I've misunderstood your question, please let me know.