Thank's for your answer. 
This is what I asked to, if there is a simple way to upgrade VC's DB 4.1 to 5.1.
So I have to install old VC's DB 4.1 before installing VC 5.1 and when the installation ask me about the VC's DB I indicate the old 4.1 VC's DB..
There is no other way to upgrade a old VC's DB I supose.