Okay, it is likely that the system files are corrupted for some reason. If you are getting as far as "inaccessible boot device" it could be either your computer failed to get permission to access the files you need, or the files you need are missing or corrupt. The easiest fix that would save a lot of headache would be the re-installation of windows. However, if you can access safe boot or even a command prompt, it is possible to recover this way.