Hi Gramme aka Donna,

You cannot import already created websites as HTML.
Only as the saved .web file

If your backup of C: was created before you created and saved your site .web file, then you have no chance at all of retrieving it I'm afraid - you will have to recreate the site again, but at least you have the online version to copy from
Xara support folder is a folder created during site export and preview which holds files such as animated gifs or flash (swf) files which you are using via placeholders.

If your backup was made AFTER the .web file was saved and you simply can't find it - you can use Windows search for *.web or download the really fast and excellent 'Everything' search utility from voidtools.com