Electrosk8r :
Dragonburn :
have you tried using the installation media, or downloading an ISO of windows 8.1 and creating a bootable cd or usb stick and then performing the install as an upgrade using the key you have been given?
No, I haven't tried that yet. Can you give me a tutorial, please?
Ok, if you have the installation media, that would be the easiest method, for that you just need to insert the CD/DVD into your drive and then reboot the computer (make sure that your system is set to boot from the CD-ROM otherwise you will have to press F8 to get a boot menu at the BIOS information screen when the system reboots). After the installation starts, select upgrade instead of custom, so that way you will retain all your old files etc...
If you do not have the installation media, you can download an ISO file from Microsoft at this link:
http://technet.microsoft.com/en-us/library/windows-8.aspx
I would recommend another program to mount the ISO file as a virtual drive on your system, this software is freeware from Slysoft - Virtual Clone Drive - you can download it from Slysoft at the following link -
http://www.slysoft.com/en/virtual-clonedrive.html
Now, for the final part, you will need to create a bootable usb stick (make sure that the usb stick is at least 8GB, most of the 4GB usb sticks run out of room). Insert the usb stick and open an elevated command prompt (right click cmd.exe and select run as admin).
At the command prompt type the following commands:
Diskpart
list disk
select disk 4 (or whatever number corresponds to the usb stick)
clean (this command formats the drive, so be sure to remove any files off the drive that you want to keep and make sure that you have selected the correct drive)
create partition primary
format fs=fat32 quick
active
assign
exit
After you have completed that process, mount the ISO file using Virtual Clone Drive (right click the ISO file and select Mount (Virtual Clone Drive E: or whatever letter is listed there) and copy the files from the virtual drive to the USB stick.
After completing this, leave the USB stick in the system and at start up press F8 to get the boot menu and select to boot from the USB stick, then follow the same instructions given above for the installation media option.
I hope that this has been helpful and let me know how you go.