I have a problem with my office pc, the problem is User Account administrator type is lost I try to restart it but it only one guest user account appear how to recover my admin user account so that I can do system restore because with guest user account I can not even open system restore because it says "you do not have sufficient security privilages to restore your system. .....", please help me how to recover my admin user account back to where it should be by the way im new here thanks for any help and im very apreciate it

Your easiest route to accomplishing what you want may be to use System Restore after you Re-Boot your machine into SAFE Mode.
Most often, folks have not set a password on the default ADMINISTRATOR account that appears when you boot into SAFE Mode.
So once in SAFE Mode you will most likely be able to select ADMINISTRATOR and from there make a selection from System Restore.

Post back if you have questions about booting into SAFE Mode, or using System Restore.

Note: there are other long and tedious methods to accomplish your purpose, but they all first require ability to log on with an Adminitrator account. A slightly less tedious plan of action, if you find no joy with System Restore, would be to create a New Account with Administrative privilege, and work from there.

Best Regards

Is this your (personal) computer or your employer's computer? If it is owned by your employer and you just use then you probably don't have administrative access. If it isn't a computer that you are responsible for (ie one that you just use) I would contact the pc techs there as they should know who is responsible for it.