I have latest versions of IE and Firefox (FF) on fully-updated XP Home.  I also have Adobe Acrobat 6 and a version of Acrobat reader.  I don't want to get a newer Acrobat, as I don't need one and frankly, after struggling with their piss-poor backwards compatibility and all their poorly designed updaters and uninstallers,  I'd climb over Microsoft to shoot at Adobe.

Anyway, If I double click on a pdf it opens in the Acrobat Reader, which is fine, as it takes less time to load than the full version and opbscures less of the page with menu bars.  However, when I open a pdf inside a browser window, it uses the full version of Acrobat.

 How can I instruct a browser to use the acrobat reader instead of the full version of Acrobat?

In Firefox (3.0) you want Tools > Options > Applications and you can change the application for Adobe Acrobat Document. This may be different for different versions of Firefox.

I'm not very familiar with Internet Explorer but I would imagine it uses Window XP's file associations which you can modify by opening any file browser window, such as "My Computer" and go Tools>Folder Options>File Types and locate the PDF file extension entry. But if Windows is already using the correct application then are you sure the IE is doing something different?

Ta for that - located it in FF.  Now it opens a pdf in a new Acrobat Reader window, rather than in the browser, which is actually better for me (you can see more of the document on screen).  Magically, IE does the same (maybe I got confused about it before, I usually use FF for this kind of thing as the download blocker in IE is really annoying).

This helps with a long-winded workaround for not having to dump Acrobat 6 with Vista (I have a laptop with Vista).  The problem with that is you can't print to a pdf in Vista with that version, although you can edit and save existing pdfs perfectly well, and it interacts badly with browsers in my experience.  This way, I can keep Acrobat 6 well away from the browsers and just keep it for touching up the odd pdf, or making pdfs from existing pdfs.  I use a free utility to actually write to pdf.

 Phew!  Anyway, Thanks!