linux and microcontroller

If you Like to use Linux in your Internet Cafe, LTSP is the best solution, You can also reuse your old computers even with out harddisk and also use low cost thin clients. For using old computers, you need some technical knowledge for installing Boot ROMs in your Network card. If you using a newer machine with PXE boot, Just install LTSP server and and set PXE Boot to tour Client.

A very good tutorial for installing LTSP Server You can see here