If an account has transactions and/or a current balance, it cannot be deleted. Is this why you are unable to delete the account?
You may need to enter a new account with the correct account type and transfer the balance from the incorrectly defined account, via a journal entry batch. Then mark the bad account as Inactive.
Make a backup of your data before doing all of this.
There may be more 'clean-up' necessary, depending on the current state of your data, but this is at least a start. Others reading this may have other suggestions.
_________________________
Regards,
Softrak Tech Support