Not a great problem,but the skipped file is Backup encountered a problem while backing up file C:\ProgramData\Bluestacks\UserData\Library\My Apps. Error:(The system cannot find the path specified. (0x80070003))
looked on the internet,found a work around that says add the file manually,but being not fully up to speed on computers how do i go about this ?
as mentioned the backup has completed but would be good to get rid of the warning.
tia.
See if this helps: https://support.microsoft.com/en-us/help/973455/windows-backup-or-restore-errors-0x80070001--0x81000037--or-0x80070003
That’s from 2012 for windows 7 
found this Bob http://www.reviversoft.com/answers/638729787/how-to-fix-windows-backup-error-0x80070003-
Method 1:Create the missing folder “C:\ProgramData\BlueStacks\UserData\Library\My Apps”, as listed in the error message. How do I do this ? tia.
Open up the folder:
C:\ProgramData\ once there,
Right click on an empty part of that folder and do the following:
http://screencast-o-matic.com/screenshots/u/Lh/1510786743444-49573.png
Give that folder the following name:
Bluestacks Next, select that folder and again create a new folder in there called UserData
Next open that new folder and create the next subfolder in there called Library
Open Library and now create another subfolder in there named My Apps (note, there is a space between My and Apps.
I have no clue if that will solve your problem but, that’s what the instructions spell out. Good luck.