I've tried it several times, but I just can't make it run. I just get a load of text in a dos screen, which is too fast to read, shuts down straight off, and as far as I can tell doesn't create a log anywhere. I dont even know if the problem is that it's not detecting the games, or that some dependency is missing. Can someone give me some step by step info on how to get this to run? The official wiki just gives some compilation instructions, and nowhere is my current problem addressed...

Try opening a command prompt manually, and starting GemRB from there. This should give you a chance to read the text.