I recently discovered a tool that can securely wipe HDDs from a floppy called
HDDErase. It is regarded by security experts as the fasest and most secure software method of completely erasing a HDD, since it utilises a built in security feature that is on most hard drives manufactured after 2001. Block wiping tools like Eraser and DBAN may take several hours or even days to wipe a drive (depending on capacity) and may not erase all data including boot sectors and partition information. The caveat is that HDDErase can only recognise drives on the primary and secondary IDE channels. So, if you have a SATA drive, you must change the settings in the motherboard's BIOS to run it in IDE or Native IDE mode.
I completely secure erased a Seagate PATA 40GB drive in around 15 minutes. It was surprising. I wish I had found this tool earlier, as I had previously used
Eraser (block wiping using DoD, Gutmann) which would have taken several hours. So far, I have not been successful in erasing a WD SATA drive in this manner, which makes me wonder whether WD drives have the inbuilt security feature or not.
Before that, I would try to physically destroy drives to damage the platters so as to prevent data recovery. Computer parts recycling is not as common here in Australia, but I do my best to ensure HDDs and other components are ecologically recycled or resused instead of ending up in standard landfill.
EDITed.