I am trying to install windows 7 64bit on my compaq presario a900 laptop. It originally had vista home basic running. I removed the hard drive, plugged it into another computer where I made the whole drive 'unallocated space'. I've then formatted it as NTFS. so, basically we are looking at a completely clean hard drive. I return the hard drive to my laptop. I then boot from DVD and start the windows installation process. the screen tells me 'windows is loading files.' I then get the windows animated logo come floating in. the logo 'pulses' for a while (as is normal), then the screen goes black with a white mouse pointer. At this point the whole system reboots and the process starts again. Endless loop! I've just tried installing Windows 8 as well. Same loop. I get to this install stage where the balls are looping and then the system restarts. The next stage should be where it asks about keyboard, language, country etc and then which hard drive you want to install to. Doesn't happen. Just reboots into the loop again. also set the bios back to default. I did forget to mention that in the past I have had Windows 7 64bit running on it, I just wanted to go for a completely clean install. Windows 7 32bit doing exactly the same. run a hard drive test and a ram test in bios. All clear. I'm more than a little confused at this point!