Revision control freeware

I am looking for a freeware which will install at server side to control file’s version. Any software will do this for me. My company is not a IT company, they don’t really understand about why we need version control for files in the server.

For those who work in development team, may understand my view of the version control. If you are having small team which only content 2 programmer, you might not having file version problem as they can work closely to resolve this problem.

As my team is growing bigger and I need to keep track on their source code and version. I need to use revision control software to do so. Any one using please send me some comment on this.