Make a disk image backup using bootable removable media. My preference would be for the image backup to reside outside the computer. If the machine does not have an internal CD or DVD burner, use an external model (which means adding drivers for the external burner to the list of software you need up-front). Another options is to copy the Windows partition to a hidden partition on the hard disk.
Make a registry backup too.
Credit :Michael Horowitz : http://www.michaelhorowitz.com/removespyware.html
