Don't worry if you see failed attempts to upgrade to Win 10

[HansV]

If you have reserved Windows 10, you may see failed attempts to upgrade in your Windows Update history. There is no need to worry about this. Microsoft Update has already started to download parts of the new OS, but it won't be installed until you have received a notification and assented.

The folder used for this is C:\$Windows.~BT. If you see this folder on your C: drive, do NOT delete or modify it.

[Rudi]

Thanks for the headsup!