Anyone here who did this before? I found this Tutorial but it just don't work.
Any help is appreciated,
Use easy transfer to back up your data and do a clean install
What you're trying to do is unsupported by Microsoft and I'm sure they made it hard to do.
On top of that your changing the software version, which won't go well probably:
How-To-Geek also wrote a post about doing what you're asking but in the end he notes:
Note: I know your not asking for this answer, but the worst that can happen is that you loose some settings and have to reinstall some applications. However, everyone using the RC will have to do a clean install
An upgrade across "milestones" is not officially supported by Microsoft, so any article you find like this is very risky to use and not recommended. I would just use the built-in Windows Easy Transfer to keep files and settings then do a fresh install as recommended.
Microsoft also stated that upgrades to Windows 7 from the following operating systems are not supported:
Further reading in the Windows 7 Upgrade Paths.