HP DC 5000 mt RAM not recognized

I got this computer (HP DC5000MT) with no ram or hard drive. So i picked up a used hard drive and ram all of which(including the computer) was to be working before I received it. But when I installed the ram it just beeps 5 time at me which according to ( http://bizsupport2.austin.hp.com/bc/.../c00066037.pdf )means that the ram is not being recognized. THe ram I got is 1 gb DDR 266 MHz eec . I tried all the slots just to be safe but It still just beeps.

Does anyone have any ideas what is happening?