I unexpectedly deleted my user account (the only administrator for the machine). I have another account which is standard account now i cant access my hard disk or anything with that standard account it is asking for boot password. Is there any way i can get back access to the administrator account?
You can use the recovery console and boot as root this is a extra option on your grub menu and create a new user then add them to the admin group. I'm not sure if this will fix your issue, but give it a try and let me know.
You can use recovery mode to add the standard user to the admin group (which is now called sudo in 12.04). Below is a set of simple instructions copied from my personal website.
Using Recovery Mode To Add Users To The Admin / Sudo Group
First shutdown your computer.
Use the following command to remount the drive
You should now see a message saying 'adding user' followed by 'done'.
EDIT: If it is telling you that user xxx does not exist, first you can use the following command to list users and make sure that you have the correct username
The other option is add a new user, from recovery mode using the following commands :