How to unlock your computer without the password

I click on the hd hard drive and change the settings to no one can read or write now I had problem to open the computer as soon I start it became gray screen so I re-stall the software and as soon I back up the computer is asking me the password I type it and can't enter after keep asking me the password is wrong how I can get back to the computer in this case your help will be well appreciate thanks jrod