you cant use a hd2o. but there was a software startup init that was used for 512k macs to use hfs 800k floppies and hd20s if u could write it for gsos then maybe u could use it. having said that, a internal hard card for a gs is ten times faster. you might not like me saying this, but a hd20 Is more valulcale as a mac 512 hard drive. as it's the only common option for said machines. on the other hand i have said its near impossible. so may that give u the motivation to prove me wrong. especially for the 2c.