That said, the HP ProLiant MicroServer Gen8 boxes are fantastic little prebuilt boxes that are very close in form factor to what you have.
Now I'm in doubt if go with a New HP where I have to also find the license and some HD or go for an used one, older but already with Win7 Pro and 2T http://www.subito.it/vi/189342896.htm
Hp ProLiant Microserver N36L
2 Hard disk of 1Tb total 2Tb
2gb Ram DDR3 ECC