A re-boot after change of these registry keys is not necessary.
he version name to be entered must be identical to the version name on the installation DVD. See here the differences of an English and a German installation
Attention: In Windows 7 Ultimate Build 7100 (Release Candidate) the effort is greater. First the entire DVD content must be copied to a folder to the hard drive. Then open in subfolder "sources" the file "cversion.ini" and change the entry "MinClient=7233.0" to "MinClient=7077.0". Then you can start the installation with "Setup.exe" (one folders hierarchy up). After the installation the entire folder can be deleted.