Anyway to force the game into 4:3 aspect ratio at full screen? Since there is no way to push it into true widescreen, i'd rather be able play it in the original aspect so that it doesn't look so stretched.

Also is there a way to reassign keys and allow task switching?

Perhaps, something from this thread?

Tried various things in that thread, but it doesn't seem to have anything to do with running TR1 in 4:3 mode, but more to do with trying to force the game into higher resolutions. Though still 'stretched' or some cases misaligned if I was reading the posters correctly..

As for resolutions. For whatever reason, I don't seem to see much of a difference, when I was messing with the settings and trying to force it into a higher mode.

Yes, higher resolutions, but I read it as the screen was still in 4:3, not always centered.

I'm unable to be more specific as I don't have the game. Perhaps it's a more generic dosbox scaling issue.

Do you have GPU scaling on or check if the monitor is scaling. I wouldn't think that would matter with the right dosbox settings but ...

Last thought, try nglide and see if it is easier to set the resolutions?

I know it's pretty stupid for me to necropost on a year-old thread, but perhaps I may be of help to someone passing by.

Check the control panel of your motherboard and/or your graphics card, it should have an option somewhere to set scaling. For example, what I did was to set scaling to apply to the GPU and not the screen; after that, every older game I played never did that horrible stretch to widescreen.
(sorry I'm not anymore specific; I'm Italian and my control panel is in Italian, so I'm not sure what the options are called exactly in English :( )