After installing turboTax, all my pdf icons turned into little TurboTax hats!
The way to change them back to Preview Icons is to select a pdf file, choose [ Get Info ], then under [ Open With ] choose [ Acrobat Reader 5.0 ], then select [ Change All ] , then go back and select [ Preview ] , and choose [ Change All ] again.
That sets your pdf icons back to the Preview application.
Stupid TurboTax!