Admin user account gone

Hello,
this is my problem 3 days for now, can you help me with this problem, im using a acer laptop, when a shut down my computer and then i turn on again my admin user account was gone and the guest account only is in their, but when i try to change my account name, then the admin appears and tells "please enter password and click ok", but i cant click the OK button only the CANCEL.(this is in the guest account cuz my admin was gone.)
but my files are still there but when i click my folder there's going to pop up and said, "please click continue to see the folder" then i click the continue admin pop's up and still i cant click OK.
how can i solve this. plss help..!!!