Simulator problem

Hi Im new to this site so this i my first post and question. Im a 4th year networking student in Edinburgh. I am really struggling to get ns2 to work on Windows 7. I'm using it at Uni and want to use it for a project to compare and analysis Routing and QOS for multimedia traffic on wireless networks. Can anyone please give a full proof way to get this working, ive tried so many hours on so many different sites but I always end up with it failing after the install or have problems with the .bash files that need amended. Can any help please.

Also what do you think about using simulator instead? Can Opnet do a better job with its free academic version? thinking QOS/routing/wireless?

Sorry if this is this wrong forum for this