I made this from playing around with walaber's fps demo, so a lot of the code is his. Basically, I messed around with the fps demo until it worked on my computer, and so here's what I made (download attachment).
I added 2 sounds: shoot and footsteps. Whenever you move (with WASD) you run, unless you press shift to walk siliently, like in counter-strike.
I made a 3 story room to run around in, with several sets of stairs and shootable boxes, cylinders, and spheres. I wasn't sure how to code the stairs, right now if you walk over something right in front of you, you have an upward impulse, which helps you up the stairs.
As for the shooting, it's practically unchanged from walaber's demo.
Extract the rar to it's own directory, the code and media are included, I didn't include a compiled exe because of the max 1mb file size on attachments.
EDIT: one of the first few lines is a display command, set it to a resolution your monitor supports.
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HP Laptop, P4 3.0Ghz, 1GB RAM, 128MB Geforce dedicated video RAM, 60GB Hard Drive, 17" bright wide screen.
A.K.A "The Uber Computer"