Old versions of Windows

Hello,

I was prompted this morning to open CCleaner to save arround 4.5Gb of memory space.

I was supprise by the "4.5Gb". Nerver had more than maybe 1Gb.

One of the items deleted was "old windows versions" containing many files ending by "...BT...".

Why would CCleaner suddenly delete so many "old Windows file"?

Could this be related to Windows 10 which has been domloaded but not yet installed.

Thanks

Did you just upgrade your machine to a new OS?

Windows.old is your previous windows version.

However I suggest using windows built in cleaner to remove the windows.old folder