I bought a MacBook air in August 2013. Just updated to Yosemite and I get the pinwheel of death all the time and I am forced to manually shut down the computer via holding down the power button. What should I do? What's going on? Thanks
A clean install involved copying off all of your data and making sure you have backups. Then wiping the hard drive/SSD drive clean and re-installing the operating system from scratch (or clean). Then you would re-install your various software programs that you use and then restore you data.
Make sure you have good backups of your data before doing this.