You can't downgrade. What you can do is:

Restore the vB 3.8 DB, remove the vB 4 files and upload the vB 3.8 files again
Royal King Reviewed by Royal King on . Coder to downgrade my forum from vb4 to vb3.8 I'm looking for a coder that would be able to perform a downgrade from vb4 to vb3.8. Please tell me your price and msn so we can talk about it more. Rating: 5