I knew that one day someone would find a way to get rid of that annoying blue thing covering our precious logon screen in Server 2008. Luckily, the people present in this topic (this link), remanaged to find a way to do it.
However, I can make a quick summary of what needs to be done.
1. Find authui.dll in Vista, x86 and x64 respectively (depending on your Server architecture).
2. Replace Server's file with Vista's
Anyway, a HUGE thanks is deserved for the people who worked hard in order to figure out this thing. Now I can finally stick to Server... after I find my logon...