Well, I really don't know...
What a friend of mine did was back up all his files and do a new install of Home Premium.
Yes, i know this is a clean install, but you have all your files, at least. There is no other way (that i know of, and I know a lot) than a full drive backup and a clean reinstall of Home premium. In older versions of windows, you could use many different tools, but those are for older OSs. So just back up your FULL hard drive (on amazon, there's a lot of 250 GB+ Portable hard disks, use one of those. Backup takes a pretty long time, from 30 min (fast computer and USB 3.0) to 120 min. Buy a USB 3.0 for fastest results.
You can install it using an ISO file (I recommend this) on a USB stick and choose boot from USB (newer computers can do this) or put it on a DVD and boot from that. I personally did this myself, I used an ISO file and a USB. I really don't recommend buying a Windows Installation Disk and choosing the "Customized" option, because it's kinda complicated unless you're a computer geek. I mean absolute geek.
Sorry for being so long.