how to reconcile old accounts

The easiest method might be to just reconcile all existing transactions through the current month. Your opening balance would be the balance as of your last reconciliation and the ending balance is the one from your bank statement.

I would go back through this year's bank statements and confirm that all of your transactions match the statements. Figure out which checks are outstanding since 1/1/06 and mark everything prior to that as cleared.Sort by check number to see if there are any missing checks or if there could be a check from 2005 that is still outstanding.

You may have to enter an adjustment to get the account to reconcile properly if there are any missing transactions.