Enlarge the screen without changing the resolution ?

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Apple menu -> System preferences -> Universal Access.

Or you can try:

http://magnifier.sourceforge.net/

I've not tried the latter, but there are several such tools in the public domain.

It is not clear what you are asking.

My best guess is that you want the Menus to appear in larger text size.

Unfortunately the only ways to make the Menu words larger is to change the resolution or use Universal Access.

If your issue is something else, the follow may help:

If you want to magnify text and images when browsing the web, Firefox allows you to do this for each website you visit by using the CMD Plus and CMD Minus key combinations. Firefox will remember the zoom level for each site independently. Safari also lets you do this, but not on a site-by-site basis.

The size of icons and the text under them can be set in the Finder > View > Show View Options ...

Hi Charnaud,
there is a ppi (pixel per inch) change available in 'TinkerTool System 2' application - but is experimental. This'll enlarge (or shrink) the all user interface (window text, etc.).
It'll change the 72ppi (Mac standard) + or - without changing the screen rez.
Unfortunately this app. is not free...

Hi again,
if you really think that is what you need then you can just download it - it's shareware so you could try it & if you want to keep it its about $12 ~ $13.
[www.bresink.com/osx/0TinkerTool/download.html]