There are many repair programs on the market that may or may not solve the problem, (Most free) just remember to create a restore point before running them. (Two of the most popular are ccleaner and Advanced system care)
As to your problem, then you need to first make sure you have a program that can open these files, (If you already have the program try re-installing it) and then associate the files with the program, you don’t say what OS you have however right click the file and choose open with, then choose the program that is designed to open the files and set it as default for that file type. (You have now associated the file with the program)
As to shutting down, then it is probably a hardware or driver problem, so make sure all your drivers are up to date. (There will become a time when a re-install will be required but it is not as often as some users make out)
Hope this helps
Bill
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English Riviera:
Live entertainment, Real Ale, Great Scenery, Great Beaches, why would anyone want to live anywhere else (I�m definitely staying put).