Disk boot

make sure your hard drive is ok, also you may have formatted or caused an error to it. My best guess is you might need to either recover it (stick in a windows disc and run chkdsk or another recovery program) or reformat and reinstall. Your best bet is to check the connections, if thats not the case then try chkdsk, if that doesnt work take it out copy any information off it you want to keep onto another computer and reformat and go with a fresh install.