Word 2003 problem

I used to have Word 2007 but when someone fitted a new hard drive for me, he put Word 2003 on it - it being the latest he had !! - heyho. This was about 18 months ago and I have had no problems anyway.

Just lately however I try to double mouse click open a file from my documents but it opens with a quite different Word document. The only way I could open it was to right click on it then click open.

Also when I try to close one I have open, I am asked if I want to save the other new Word files I have been working on and minimized - in other words I can't just close one file I have to close the rest and save them with names where necessary.

What has happened here and how can I put it right please.