Had the same problem a few weeks ago ( https://www.techspot.com/vb/topic83740.html ) but in that occasion it sorted itself out. Whilst uninstalling a program the power died (bonehead me switched off the wrong socket) & I couldn’t boot or install Vista. Took out 250GB HDD & using old PC (which I'm writing this on) transferred about 50GB of data onto an 80GB HDD. Formatted the 250GB & put it back inside the new pc & tried to install Vista. I got the following stop message stop: 0X0000007E (0XFFFFFFFFC0000005 0XFFFFF800985E251 0XFFFFF98000A05B98 0FFFFF90000A05570) borrowed a m8's copy of 32 bit XP (don't have 1 myself) & it installed ok, so I don't think it's a hardware issue. The only change since I built the rig in March was the addition of 2GB & since it's always shown as 4 in total. any ideas?