[Need Helps] Ask about Upgrade vB 4.x to 4.2.2

[TommyHara]

Hello,

The first time, I used a vBulletin nulled script for test and built a forum from it, after that I bought a vB license from vBulletin.com

Now I want to update from vB 4.20 to vB 4.2.2 patch level 2 or 4.2.3

My question is: Do I only need to copy overwritten files into my vb 4.2 folder or I must re-install vb 4.2.2 and add license key while installing new version (4.2.2) ?

( I'd like to keep the database from vb 4.2 because I have more posts/threads on it)

Are there any tutorials to do that?

or which is best way to update my vB nulled 4.x to 4.2.2 (licensed) correctly?

Thanks in advanced!