Why can't I open my computer programs?

I can not open any programs such as my internet browser, my control panel, windows media, mcafee security system, etc. For example when i double click on any of the programs on my desktop a small error message appears instead and it reads "This file does not have a program associated with it performing this action, Create an association in the Folder Options control panel" I have a windows XP, my computer is an Acer Aspire One.