you played it as a kid, but it wasn't DOS and you're 26
"as a kid" I would guess to be around 6-12ish? so that would put the timeframe for the game to be around 1990-1996, so late windows 3.1x, very early Win95 era.
First person, but not 3d? So it was prerendered. The only games that jump to mind like that are the Myst games.
Googling around a little bit with this in mind, is it The Journeyman Project?