I have recently upgraded my laptop to Windows 8 pro from Vista - everything seemed fine and then the Live Mail came up with a message 'could not be started may be incorrectly installed or disk full' which can't be right. Looked up the problem and tried to repair/re-install and then I got the above message on almost everything I tried! Some fixes mentioned 'regedit' couldn't get into it, tried uninstalling Avast antivirus couldn't access it! Help! Not 100% with Windows 8 and not sure if a restore may help? Any ideas gratefully accepted.
window key + x select run
type cleanmgr.exe select options to clean up temporary files, memory dumps...
-also, windows 8 setup would have moved your copy of vista to windows.old
you can delete portions of it to free space or the hole thing after you grab anything you really want to save out of its directories. I would suspect that most of your used space is in this old directory.