The page for 2008 R2 Express is http://www.microsoft.com/downloads/details.aspx?familyid=8b3695d9-415e-41f0-a079-25ab0412424b&displaylang=en&Hash=Zyv%2fIlY0jMJ39QCjdf%2b0z8TewjrbmHFfVWpLFAve3vYc5BYxrjzxoa2JJRvFLWUQVoY%2f%2bqRDGstaHsYzCeQn9w%3d%3d#fil...
The File Version is the version of the setup.exe wrapper and I don't think you can specify its value in IS, however you can use utility like StampVer.exe to get this done easily.