Thanks for your replies. I have an iMac. Running Mac OS X 10.6.8. I do have the original install discs. I made an appointment with the Genius bar and right before going I tried the computer again. Booted up, moused places but the click would not work (corded mouse, tried a different mouse with same results). Drove the 22 miles to the Genius bar and, guess what, it worked perfectly. Darn, I hate when that happens. I will keep the mentioned advice and if it occurs again I will give them a try. Thanks so much for your responses. It's nice to know that help is available.