Every time I try and open any software Turbotax, Microsoft Word, powerpoint, access, etc i get an error message the application cannot be found even though it is installed. I just installed turbotax and actually used it but when I went back into it I got that message. Everytime i try to open something it asks me what program I want to open it with, I can't even open the calculator. Sometimes the message comes up the file does not have a program associated with it, create an association in the Set Associations control panel. What is that? All the programs were working at one time and all of a sudden I keep getting these messages. I have an HP Pavilion with Vista operating system. The programs install fine but I can can't get back into them. What is causing this?