Thanks for the reply :-) But it isn't quite what I'm talking about. Although I do believe I'm running with unlimited storage and all that.
The way alien containment info was stored in the original was in a file called ASTORE.DAT. It was essentially plain text file that has a list of all the aliens you've captured. Unfortunately there was a limit (file size? line limit?) that, once reached, no matter how much Alien Containment space you actually had open, you would NEVER receive another live alien. To alleviate this issue, you could delete it (or delete the info in it) and it would SOMETIMES work again, although most often the game would just continue to make captured aliens disappear.
Now, this was a fairly high number, most people would never reach it. There is more than enough room to capture all the aliens you needed to fill the UFOpaedia, unless you make it a habit of capturing soldiers. But not much more beyond that. Like I mentioned, I love capturing aliens (it's sometimes easier than trying to kill them), and I also liked really long games, so I would usually always reach that point.
I don't see the ASTORE.DAT file in my OpenXcom directory, so I'm not sure if this is even an issue. I just want to make sure before I go hog wild capturing live aliens :-)
Hope this was enough info to explain what I'm talking about lol :-P