Can I convert existing PCs to thin clients?
2X Thin client Server - a commercial solution that deploys a linux based thin client OS to existing PC's and low cost thin clients devices. You can centrally manage settings and configure to which terminal servers (Windows or Linux) a user should log on to.
PXES - This is an opensource solution that allows you to customize a Linux distribution for your network environment and then serve it out via PXE booting. PXES can boot from: PXE enabled network card, Etherboot, CDROM, Hard Disk & Flash memory. More Info:
Etherboot - similar to PXES - http://www.etherboot.org/