Is it possible to somehow encrypt the content of your entire HDD:s in such way that you would need to boot from a floppy and get the keys out of the floppy and decrypt them with your passphrase? And then go on loading OS and keeping the content of HDD:s always encrypted?

Kinda like Scramdisk or PGPdisk but somehow you would have to be able to "keep" the key to open them in your computers memory and not let Windows kill it off there at any time.

Can it be done or is hardware solution needed?