Shoutbox

I have a "problem" and if anyone knows how to help me, please respond quickly, because I'm desperate.

I used encryption to keep my chat log files safe and I still know the password, that's not the problem.
My problem is, that I would like to decrypt these files, put them into a normal form, one which does not require password every time I want to read those files. I know how to do this for the new files, it's easy, but for the existing ones?! Please tell me there's a way

Thanks in advance!