Although the solution posted by TehMarv in November 2010 still works (it's January 2015 as I type this), there is now a better and easier solution.
TehMarv's solution was to download a mod made by Ghostdog for Planescape:Torment, and copy the font files from that mod into your BG2 folder. This still works (I tested it) but it does give you a different font; the one from Planescape. It looks OK but it's very thick.
Since that response was created, Ghostdog made another mod for larger text in BG2, and it is easier to install. To my eyes, this is the best of the "larger font" mods, and it retains the Baldur's Gate font. I've attached some screenshots so you can see them for yourself.
Because my reputation here isn't high enough, I can't post a link to the newer mod. But if you search Google for "Bigger Fonts mod for Baldurs gate 2"
it will be the first result. It's at shsforums, with exactly that title on the mod page.
The attached screenshots show the Widescreen Mod at 1600x900, and this Bigger Fonts mod.
Hats off to a great community at GOG. Finding the mods I needed to play BG2 fifteen years and many versions of Windows later could not have been easier. I hope this information helps someone else. If this information is helpful to you, I would appreciate a Rep point so I can post links directly in the future. If I get enough mod points, I will put the link directly into this message. :-) Cheers.
Update: Thank you for the mod points! Here is the direct link to the mod I described: http://www.shsforums.net/topic/52452-bigger-fonts-mod-for-baldurs-gate-2