First of all, if you do not include a fee in your TX, or if the TX fee is too low then they TX may not confirm or if it does confirm it may take several blocks to do so.
There is not a setting to change the TX fees that multibit will include in the TX and the client will not sign the TX if there is not a high enough balance to pay for the Tx fee. Multibit will calculate the appropriate fee for you to get the TX included in the blockchain quickly
Like I said in my original post:
Yes, I know that if I do not pay any fee for a transaction it might take forever (did once using blockchain.info android wallet and it took 3 days to get 1 confirmation).
I just want to find if it is possible with multibit, maybe by installing an older version.
No, there is no setting to not send a fee with multibit.
The only way around this would be to export your private keys and import them into a wallet service that does allow you to manually adjust the TX fees. You could then use that wallet service to send a TX when you want to adjust the TX fees and the TX will show up on Multibit, although it does sometimes look a little weird when you do so (just make sure that you set your change address to an address that is in your multibit wallet)
