MerpsMom,
We can handle this right here and now. Here is what you need to do to modify a file associaton:
1)In My Computer or Windows Explorer, on the View menu, click Folder Options.
2)Click the File Types tab.
3)Click the file type you want to modify, and then click Edit.
4)Click on the command you want to modify (probably open) and then click edit
5)In Application used to perform action, enter the command that you want to complete this action (this would be your POS command,) and then click OK.
I'll email you with some contact info if any of this doesn't make sense.