In this video "how to" Dan Wahlin walks through the steps required to install and configure Subversion to control your .NET source code revisions. Several commercial options exist for source control of course such as Vault and Microsoft's Visual SourceSafe to name just two. Subversion is an open source project (it's freely available) and has excellent documentation and support available. It's also easy to use through the command-line or through TortoiseSVN.
In the video you'll see how to install Subversion, configure it, install the TCP/IP service, and add new or existing projects into the source control repository. You'll also see how to use TortoiseSVN to create repositories and manipulate files in a Subversion repository. Although the video discusses installing the TCP/IP service for accessing a repository remotely, it doesn't cover how to access the repository through HTTP. You can find more information about that task and how to configure it with Apache here.
Links mentioned in the video are included below:
Subversion Project Site: http://subversion.tigris.org
Rick Strahl's Step-By-Step Subversion Article: http://www.west-wind.com/presentations/subversion/
Subversion Online Book: http://svnbook.red-bean.com/nightly/en/index.html