Microsoft is a big fan of defaults for just about everything from default fonts to default printers. They also like to use default locations in their Office line of software. They choose a default location for you when you install Office on your computer but fortunately they allow you to change this location if you don't like the default.
You may have noticed that when you click on Open in Office that it most likely opens to your My Documents folder by default. It also defaults to this location when you click on Save. If you store your documents somewhere else and want Word or Excel etc to open and save to that location by default then this is easy to change.
In your Office 2007 program click on the Office Orb and then on Options. For Office 2010 and up you would click on the File tab and then Options. Then click on Save on the left hand side. Next find the Default file location box and change it to the location of your folder where you keep your files. You can either type the path or click on the Browse button and browse to the folder and then click on OK.