How do I get rid of ‘Choose the program you want to use to open this file?

How do I get rid of this annoying popup in Windows 7? Also, I get another popup when I try to open some files that says FIND or SAVE instead of the usual OPEN or SAVE. There are files I just want to read, not save. BTW this just started happening recently. I’ve tried everything I know to no avail.

Thanks. Joanie