reset administrator's password:-

beware this tricks works only when you logged on on your machine as an "administrator"

1st method: If your account has administrator privileges you
 can simply reset the password
Click start >
right click my computer >
manage >
click local users and groups >
users >
right click administrator >
set password and enter the new password twice.

2nd method:
click start
in search box type cmd
right click on cmd and choose run as admin

the command prompt should read
C:\Windows\system32>

type "net user" (without quotes)

it will show the current names of users 

Now you type
net user "user name" *

(quotes if the user name is of more than one word and without
 quotes if the usename is of one word only)

type the new password:
retype the new password:

now you are done!!!