Hello,A few questions.You say you tried to 'reboot', how did you do this, start menu - restart? Also, you say you 'had not done so in a while'. can you elaborate on this? There are many possible problems, one option I would try would be to boot from usb with a copy of linux. You can easily turn a usb drive into a bootable with ubuntu. If you are comfortable enough to do that, you are then able to rule out the HD. You are now able to attempt to use the grub boot menu. This should give the option of booting into windows or ubuntu at start up (you may need to actually intall ubuntu to get this option).I am unsure exactly how I encountered this problem, but I had somehow lost or corrupted the file the told windows to boot. When I installed ubuntu and used the grub booter (this is default when installing side by side dual boot) it worked fine again. I also had the joy of playing around with linux. One day I decided to uninstall linux, now no longer had grub, and ended up in the previous situation again. So this is not an optimal fix for most. It will however let you know your HD is operational. =)There are many options for you. I hope my story helps you, if nothing else you will learn a ton in the process.