2.6 is backwards compatible though, meaning that the DLLs contain supporting code for 2.5 and 2.6. If I have 2.6 on my machine and distribute a project with 2.5 reference set you should be able to run the app as long as you have 2.5 or higher.

Nilesh, the easiest way to check if you are not distributing the highest MDAC (as Eric says, check your redist folder), is to just install MDAC 2.6 on the client in question. If you install 2.6 and it starts working, you know your VB is not packaging with the most recent version.