there are alot of solutions depending on your requirements.
do you need to be compliant (e.g. PCI / SOX etc...)
Do you need two factor with a token ?!
here are just some options:
free:
www.truecrypt.orgenterprise:
www.checkpoint.com - FDE (Full Disk Encryption) formally Pointsec for PC, also available now via
www.zonealarm.com for home users
www.safend.com - Also offers FDE with its own advantages