$10-15 per adapter, plus $2 per drive, is $12-$17 per 40GB, get 4 of them going and you could have bought a cheap 500-750GB.
Those adapters are flaky too, picky on the type of drive, type of motherboard, half won't boot off the drive, and as stated, those drives are going to be slow, regardless of being new or not. it's not worth it IMO.