Ok, thanks to people's help I could finally play the other games in this computer (Thanks everyone!), but now I seem to have a small problem...
Most of you may know a level alled "Never burn money", from Marathon 1, where we need to collect 3 chips. Getting the first 2 is easy, but when it comes to the third one, there's a slightly longer path to take.
I took that new path, eventually reaching a room filled with enemies. In there, I pressed two switches, two a big elevator slightly up, and then a smaller one to the top, where I killed 2 enemies. There's a switch nearby (probably the one who opens the area where I am supposed to end this level), and this is where my problem is... I accidentally pressed the button *again*, while it was doing... whatever it was supposed to be doing.
It became deactived, I thought it was fine, and I saved the game before continuing to search for the final chip. However, when I found it, there was a big problem, as shown in the image below:
http://img405.imageshack.us/img405/2870/mrfy6.jpg
Basically, the door didn't fully open, and I can't enter there, to get the final chip and gain access to the console. Is this a known issue? How can I fix this, to complete the level and advance in the game? Do I have to start it all over gain? >_<