GPm files

Presumably, you mean GPX and CSV files.

CSV files will open natively in Microsoft Excel.

You will likely need to down some software such as Extra POI Editor, MapSource, BaseCamp, EasyGPS, etc. if you want to open GPX files on your computer.

Note that it is not necessary to OPEN the files on your computer if you want to LOAD them on your GPS unit. You only need to SAVE them on your computer.

What exactly are you trying to do?

I don't like to do so, but I have used Office to make changes to .gpx files. Office opens them as if they were XML files.

As MM said, what are you trying to do with them?

Hold down the shift key then right click on the file. A sub menu will show, then select 'open with' then select the program you want to use. You can then set that program to be the default program, but be careful as then that program will always be the one to launch for that file type.

Both are simply text files. If you really want to see the files in their natural form, just open them in a text editor.

Your confusion about the extensions is likely because you are letting Win 7 hide the file extensions from you. That is never a good idea and can lead to lots of problems. To fix this, just open any folder, then go to Tools -> Folder Options -> view tab and there, under Advanced Settings, uncheck "hide file extensions for know file types" and then hit Apply or OK.

The reason that the programs you mention are started is because those file types are already associated with those programs, but you can change that and associate any file extension with any program that you have installed.