A version control system

TortoiseSVN
Free
Offline
http://tortoisesvn.tigris.org/

TortoiseSVN is a really easy to use Revision control / version control / source control software for Windows.
Since it's not an integration for a specific IDE you can use it with whatever development tools you like.
TortoiseSVN is free to use. You don't need to get a loan or pay a full years salary to use it.