In Windows 7 you can fine-tune default programs based on the file type or protocol by changing file association
1.Click Start then type programs in your search box then press Enter
2.In the right pane,click Associate a file type or protocol with a program
3.Scroll down to find and select the file extension whose association you want to change,then click Change program….
4.Choose a program from list(or browse to choose a program) to change the file association ,then click OK