Well, realistically the size of the screen doesn't matter: it's the
resolution (640x480 pixels, 800x600 pixels, 1024x768 pixels, etc.), but I
know what you mean.
Access on its own cannot do it. You need to add code: either code you write
yourself, or an add-in.
You can learn how to write your own code to do it from whichever Access xx
Developer's Handbook (from Sybex, by Litwin, Getz and Gilbert) is
appropriate for the version of Access you're using. Learn more about the
books at
http://www.developershandbook.com/ (or you can download a free MDE
add-in which will let you do this from
http://www.developershandbook.com/downloads.htm)
Another option is to purchase ShrinkerStretch from Peter De Baets
http://www.peterssoftware.com/
There's also some code at
http://jamiessoftware.tk/resizeform/rf_download.html but I don't know
anything about it.