In Romans 7, Paul is discussing his desire to follow God's rules (I love God’s law with all my heart. But there is another power within me that is at war with my mind. This power makes me a slave to the sin that is still within me. Oh, what a miserable person I am! Who will free me from this life that is dominated by sin and death? Thank God! The answer is in Jesus Christ our Lord. So you see how it is: In my mind I really want to obey God’s law, but because of my sinful nature I am a slave to sin.) This would seem to be indicating a post-conversion Paul writing about the fact that he is still falling subject to the trap that is presented by sin. The only way to overcome such temptaion and power, is through the Holy Spirit. It is not an instantaneous work, but rather an ongoing journey of the Lord working in us until the day that He completes us, and gives us that victory over sin.
There are some who would argue that this is a pre-conversion Paul writing about these things. Personally, I do not see how that would be feasible, given the fact that he says he loves God's Law with all his heart, and the answer is in Jesus Christ our Lord...Pre-conversion Paul was a very strict, stanuch, Christian-persecuting man. This does not seem to be in line with the words that Paul is writing here, which would indicate that he is still feeling those pressure even after his conversion. This is what I would say also most closely aligns with my thinking, rather than the assertion that the freedom from the temptation and powers of sin are instantaneously broken upon conversion for every person, every time, always.