I'm using the 64 bit ver. of Freya and I have an AMD HD5770. I installed the latest driver provided at AMD website. Now this driver is 64 bit only and 32 bit games don't run. I need to know if I can install the 32 bit driver similarly and not break anything. I know the repository's proprietary fglrx contains both libraries but I just wanted to use the latest drivers.
This is a bit technical, so let me know with a comment on anything you get stuck with but here goes:
Your 32 bit games might not be failing because of your driver but because 64 bit Ubuntu doesn't ship 32 bit libraries. there used to be an easy metapackage for 32 bit support called ia32-libs but for whatever reason it was removed.
To work around this go to your game's folder in terminal eg
~/games/foobar and in it type
ldd foobar using the output to find the missing libraries. You can then install the 32 bit versions of them. As an example for sdl2 you'd type
:i386 denoting the architecture. You could theoretically install arm libs this way but they won't run on your processor.
apt-cache search foo will probably help you alot here.