[Blind-sysadmins] thin clients and Linux

Hi, I am in the research stage but I was wondering on peoples thought of converting thin clients to small Linux machines. A contractor here in the place that I live sold me these old Hp thin Clients for about 10 dollars apiece and I was thinking of trying to either upgrade them to 7 or run Linux. So my questions if I were to upgrade them to 7 how much would the licenses cost to do this If I were to install Linux could it be done. I know how to install Linux but I guess I am asking is there anything I should be aware of when trying to install Linux on a thin client?