how can i do reset administrator password?

Windows 7

From the Start menu, select Control Panel. If you are not already in Category View, in the upper left, click Category View. Then, click User Accounts and Family Safety.

Under "User Accounts", click Change your Windows password. If prompted, click Continue.

Under "Make changes to your user account", click Set a password.

In the "New password" and "Confirm new password" fields, enter the password. Click OK twice.
Windows Vista

From the Start menu, select Control Panel. If you are not already in Classic View, in the upper left, click Classic View. Then, double-click the User Accounts icon.

Under "Make changes to your user account", click Manage User Accounts. If prompted, click Continue.

From the Users tab, click the name of the administrative account, and then click Reset Password... .

In the "New password" and "Confirm new password" fields, enter the password. Click OK