i found this on the espn website:
Proof of time
disney princess half marathon
if you believe you will finish the half marathon in less than 2:45 hours, proof of time is required for start corral placement.
Please provide proof of time at the point of registration.
Proof of time should include name of race, year, distance and time finished (i.e. 2009 boston marathon - 3:35 or 2010
disneyland half marathon - 2:25). If you do not have a proof of time to submit, list n/a at the point of registration. Half marathon proof of time must be from a race 10k or longer. All forms of proof of time must be from a race after july 1, 2008. If you do not provide proof of time you will be placed in the last start corral.
If you do not provide proof of time at the point of registration or acquire it after you have registered, then email this information to disneysports@ trackshack.com before december 27, 2010. After december 27, 2010 you will need to bring proof of your estimated finish time to the runner relations booth at the expo if you wish to have your start corral placement changed. If you listed a race result as proof of time when registering online, then you do not have to do anything further.
Hope this helps!