The GOG version of TR1 from TR1+2+3 worked without tweaking on my Windows 8.1 computer.
However getting it to work with glidos http://glidos.net/install.html
and using the enhanced audio and texture packs and the restored FMV movies from the Playstation version was another matter. The enhanced audio and textures were actually not difficult to configure using the instructions on the Glidos website. But I had to install a codec pack (***Windows Essentials Codec Pack***
) to get the FMV movies to work.
You get the texture packs fromhttp://www.tombraiderxtra.com/
Some are only for certain levels, so if you want to use different packs for different levels, you exit the game and choose the texture pack you want to use from the dropdown in the Glidos configuration.
However in the end I got a much much better looking TR1 than just the straight-from-GOG version.
Glidos has instructions for the GOG version, the Steam version, and the CD version of TR1.