http://en.wikipedia.org/wiki/Data_recovery (section titled overwritten data).
SSDs may be more of a risk.
Not really - the secure erase command implemented on most SSDs will really
erase all the data on the drive in a few seconds.
Secure erase on conventional HDDs is less reliable.
The answer, of course, is to use an encrypted drive where a digital key is required access the drive. Overwrite the key stored in the controller and the entire encrypted disc is useless.
Such discs were invented years ago but nobody bothered to use them and software encrypted drives (like the one I am using at this moment - work PC!) have only become common recently.
Strangely, when this PC is replaced I am still expected to use a secure erase packiage to wipe the disc - they obviously don't trust the encryption!
Ex <n>ildram , been to SKY MAX - 15,225 Download
BE Unlimited - 21,000 Download 1,200 Upload,
Moved house, now BE Unlimited 6,500 Down, 1Mb/s up - gutted!
FTTC Cab installation commenced 12th April - expect full 80 / 20 - bye bye BE, hello BT Infinity soon!