You'd be surprised what creditors will do for you. I did the exact same thing about a year ago, wrote a letter to a couple different creditors pleading for a goodwill adjustment to their records and was able to get ALL late payments I've ever made to all of my creditors changed to show paid on time.
It just takes perseverance and a lot of time, likely at least 3 months.
I say go for it, it will never hurt to try. Nico, check out this thread of mine for some sample goodwill letters, they are a couple posts down from the top:
/threadview/2186.html