Batya

I recently bought Compaq Presario CQ40-115AU in which there was installed Windows Vista. Processor is Amd Now I want to downgrade to Windows XP but I can't install it. I tried many versions of Xp but none of them helped. in most of them blue screen of death is occurring code: 0x0000007b (0xf78de524, 0xc0000034, 0x00000000, 0x00000000) or even it isn't start installation process just a black screen Has anybodyhad same problem, if yes can u help me? I searched on the internet, i read about nlite'ing something into the windows Cd but i have no idea how to do it and so.... Thanks in advance!