I had a buggy problem and decided to try a system restore to a point in time 2 weeks earlier. Everything seemed to go fine until the system restarted. It would get past the "starting windows" screen, then act like the desktop would reappear next. Nothing. Just a usable cursor and a faint glow on the screen. I tried to start task manger and it froze. Did a hard boot, same response except task manager is no longer an option. Ran diagnostics and everything is fine. Tried booting from the Win7 disk...nothing, no boot. The only disk it will boot from is the Dell diagnostics disk.
Other stuff to note. The system seems to continue booting even though there is no desktop etc. I can see the wifi make contact and the controls seem to work. Just no usable operating system. The original buggy problem I had was no video play on You Tube...so my course of action may not have been a good choice anyhow.