Remove Password using Manage

First Boot from a windows DVD

Then Repair --> Load Drivers

Now Open Desktop 

My Computer Right click 

--> Manage

--> Local Users and Groups

--> Right click user name

-->choose set password

--> Choose Proceed

--> Enter New Password

--> Now Press OK button

That's all Now Remove DVD and Boot from Hard Drives.

If Windows DVD's couldn't Run manage you can download ERD bootable .ISO images and burn to DVD's then boot from it.

Windows XP ERD

Windows vista ERD

Windows 7 ERD

Windows vista ERD