I know the best answer has already been selected but I thought I would throw it out there that it's far easier to wipe all your data and go back to factory defaults. Wibdows 8 has this feature built in. Here is a paste from a previous post that I solved:
With Windows 8.1, Hold the left SHIFT button, then press restart. This will load a windows troubleshooting section. You can then use the reinstall windows function. If it was installed properly first time round, it shouldn't require any extra data or CDs, nor do you have to do anything too technical. There is a simple wipe or secure (DBAN-Style) wipe feature that you can literally just press and leave. When it is finished, it will go back to factory defaults.
Hope this helps!