That's what I want to do. But I'm slightly concerned that if I delete windows.old that my computer may get damaged etc. I certainly do want to free up significant space as the folder is 10GB! What would happen if I deleted windows.old? Would anything happen to my PC (Apart from windows.old being deleted)
You would effectively delete the old program files of your pre-upgraded computer, probably nothing that didn't get swung over to the new operating system.
I've done it multiple times with no problems.
If you have logs of your taxes through a tax program on that .old, you make want to salvage that data.