Can't get the door to Episode one open

[cptgse]

The directions say that you can just walk thru the door. This does not happen. Is there something else that needs to be done first? The game seems to load correctly. Am using XP Home SP2, ATI Radeon 9200 SE. Have 1 gig RAM. using Intel. Pentium 2.4 with 1 meg L2 cache.

Everything should work. Why not?

Thanks