If you have managed to get this far without problems, then that's great. Chances are that you won't have any problems at all because vBulletin has been designed to make installation quick and easy.
However, it would be unwise to discount the possibility that things could go wrong.
Here are some of the most commonly occurring problems that you might encounter during the installation of vBulletin
This is the commonest issue that you are likely to encounter and isn't really a vBulletin problem—it just means that you haven't made all the necessary configuration changes.
If vBulletin cannot access the database, check the following: