Your issue has nothing to do with a config file. Your issue is under the FAQ forum one of the common installation mistakes a user makes look here number 5. vBulletin Installation/Integration Common Issues and Resolutions.
Either you have not input the correct vb
database when you specified the user database or on step 4 of install you did not enter the correct vb
table prefix of your vb
tables where asked.
Your issue is one of those absolute errors which makes it also very easy to spot.