Darik’s Boot and Nuke (DBAN) is excellent free utility which can securely wipe computer hard drives. It works from a bootable CD/DVD so is completely independent on client operating system.

Recently, when I tried to wipe couple of DELL XPS laptops, DBAN got stuck while booting:

Darik’s Boot and Nuke 2.2.6 (beta) is starting.
Waiting for USB devices to register…………………………….done
PCI (sysfs)

Issue was caused by an SD card reader. To resolve the problem I had to enter BIOS (F2 while booting on DELL machines) and disable Media Card and 1394 under Onboard Devices.