Since your F-2 visa has now expired (hopefully, very recently) and you are still in the US, you will now be considered/classified by USCIS as an "Overstay" and will be required to consular process back in your home country for a new F-1 student visa in order to be able to return to the US to attend school rather than having been able to timely file for "change of status" prior to the expiration of your F-2.
Answered on Jul 25th, 2012 at 3:52 PM