I recently had to use cmd to format my C: due to viral infection. Once I did that, i booted up the old windows XP install disk via external dvd drive. I chose the C: to install XP (my plan was to install xp then upgrade it with win 7 because when i tried just installing windows 7 it would say "cannot install windows on this partition because the disk might fail soon"). So everything would go smoothly from there, it would restart then i would eject the disk so it would boot from the hard drive (in the BIOS i have the external drive first and the hard drive second) however when the SATA is set as ACHI i just get a black screen saying error loading operating system amd when the SATA is set as IDE i get the same black screen except this time it just says " Error reading disk. Ctrl+Alt+Del to restart. However no matter how many times I do this it just does the same thing. I also know that it isn't the windows files b/c when i reboot the disk it says that "there are already windows files on this disk, would you like to format...." Does anyone know what is going on, why, or what I should do about it?