if you have administrator's privileges you can do it this way:
Hit the Enter key
A programm will open, on the left click on the Users and then on the right right click the <i>Administrator</i> account, then seect the change password menu.
If you are not a member of the Administrators group you can do this by using a <a href="http://www.ubcd4win.com"> UBCD4WIN LiveCd</a> that enables you to boot from cd and then use a password tool.
I hope this helps