Stubborn apostrophe won't show!

How can I get my system to recognize the apostrophe key with a single hit?

My apostrophe (') won't show unless I type in another character, hit space bar or enter key. This occurs in all software programs - word processing, spreadsheet, email and CAD.

At first this was a nuisance problem I thought I could ignore, but in CAD programs it makes it impossible to use this character which is important for representing Feet. Any attempt to hit space bar, enter key or make a double apostrophe entry then backspace always nullifies the CAD command.