If possible run a system test from bios for your system RAM,or temporarily replace the RAM to troubleshoot.
I've come across this exact problem on an HP Laptop running Vista Ultimate. Did everything I thought would work, replaced/tested hard drive, made multiple attempts to install operating system both XP MC SP2 and Vista. HP serviced and found the RAM chips were defective, I've never seen it before, but they said it was caused by a power spike of some sort. This is very rare since the computer is constantly conditioning the power supply through the laptop battery and the laptop had been working fine for 8 months with no prior issues. This might help, if not it's just one more thing to rule out.
i have windows XP media center edition... i have 4GB ram 3 hard drives 250GB each (western digital) and AMD dual core athlon 64 X2 3800+ one day while watching south park my computer brings up the blue screen of death.. i let it sit there for about an hour before i get tired of it sitting there and i shut it down.. i bring it back up and it says NTLDR missing... so i got pissed went and grabbed a coke and watched some TV went back installed my windows CD restarted my computer changed my bios to read the CD i went and did the windows repair thing and it said maintanance complete restarting computer to complete... well it went back to NTLDR is missing... so i found the NTLDR file put it onto a floppy disk along with NTDETECT.COM and went to windows command prompt and typed in copy a:\ntldr c: it said copied 1 file then i did the same with NTDETECT.COM and they both got copied successfully hen i restarted my computer and it booted to restarting setup i was like sweet then as it was installing devices it went from 39 minutes down to 34 minutes and then my computer just shut off and started the whole process over and it gets caught in that cycle... same spot everytime 34minutes... my computers temp is 74 degrees F and the disk is clean.. any ideas