dark_lord69 :
I would never sell a computer with a drive in it without running DBAN.
It's what we used in the IT department at the BANK I used to work for.
That wipes the drive, making the restore partition useless if that is the only way to restore the disk. If there is a restore partition on the system, I'd boot off a Windows setup disk, delete and format the existing partition, then do a restore and then you can use a program to wipe the free space on the drive. That will make getting any files from the system almost as impossible as with a full secure wipe. The restore to factory defaults will over-write the disk up to a point, doing a secure wipe on the free space will over-write the rest of the space.
But.. if there is a system disk available, then booting off a disk and wiping it that way is very secure, just needs several more steps with installing Windows clean and doing all the driver setup.