Ok I have been in that exact situation now. I arrived Jan 2007 in Europe as a tourist, and stayed and studied at an American University in Brussels for 2 years. I have made 2 years overstay of the original tourist visa.
I have left BE without any problem, and know that the scans at the airport do not tell the days you flew in, and out of the country (that's what the stamp is for).
Now there is clear documentation on my passport that I never left after 2 years.
There is a girl back there that I want to marry. I am not sure if I will get back into the country and propose to her. How is this possible that a society can keep 2 people who love each other apart. I guess cuz i broke the law. Well, I would like to move on from that and get the proper papers as well.
1) I don't plan to return to Europe for a year since leaving
2) I will get a new passport before returning to Europe
3) I will marry her immedeatly when I come back, then do what you said, go back to USA and apply for papers there.
4) Always buy round trip ticket for 2-3 weeks after entry
5) Always claim "tourist" upon entry into the Schengen.
Does anyone know if this is possible, or am I banned for 5 years ??
Most people are completely uneducated about how this works, and usually say stupid things about the return rules and 90days this and that. I know all the rules inside and out. However, I do know that Americans do slip thru the cracks sometimes.
PLEASE TELL ME WHAT HAPPENS TO YOU ! PLEASE ALSO ADVISE ME AS TO ALL PAPERWORK AND THINGS AFTER MARRYING SOMOENE IN EUROPE

Thank you so much !