Windows 8 In-place Upgrade Tip - Use the Disk Cleanup utility to clean up the old files... (i.e. There's no need to delete the "windows.old" manually)
So you've done an in-place upgrade to Windows 8? And you've noticed how much drive space that ate up? If all's working well and you're happy everything is good, you can easily reclaim tens of gig's of drive space. The Windows Disk Cleanup is your ticket. Run it in the System Files Mode
And after a bit you'll see the Upgrade Logs, Previous Windows Installation and Temp install files choices
As you can see, in my case, we're talking about 32Gb of space I can recover... NOTE: There's no going back, no undelete/recycle bin when you delete them, so be sure.
Related Past Post XRef:
Bringing back the Delete confirmation dialog in Windows 8
Adding a Windows 8 "All Apps" shortcut to your desktop/taskbar
Living with 8, my 8 days with a Windows 8 upgrade - Day 2