Best LINUX for RDP

I want to recycle my old PC’s as thin clients. I have some (but not much) knowledge of linux, I have a windows 2003 terminal server and a load of old Pentium 2 desktops and would like to know the best linux distro to use (for old PC’s) and how to configure it to pick up an IP address from DHCP then start an RDP client session to a specific server. This must all happen without user interaction and will preferably drop back to the RDP logon when the user disconnects, I don’t want them getting into the background linux at all.