Ah - I don't *think* the XP install would cause a problem - certainly not for a normal mode SFC scan, anyhow.
Typing the command into the Search box will only run it in a normal User mode - it must be run as an Administrator (perhaps that is why it didn't work before?? - no- from your second picture, it looks like it ran in Admin mode but failed. ) Booting to the Repair Environment automatically elevates your logon and takes UAC out of the equation, and reduces the potential interferences to the minimum. 'normal account' simply means for you to use the normal username and password that you log into the PC with (which is almost certainly an Admin account).
Looking in the CheckSUR log, there is a registry entry that is causing problems, as well as a few missing files
The missing files are interesting - They would tend to indicate that you should be seeing non-genuine notifications, but I can see no signs of that in your screenshots.
Please run an MGADiag report so we can check this...
we need to see a full copy of the report produced by the MGADiag tool
(download and save to desktop - http://go.microsoft.com/fwlink/?linkid=52012
Once saved, run the tool.
Click on the Continue button, which will produce the report.
To copy the report to your response, click on the Copy button in the tool (ignore any error messages at this point), and then paste (using either r-click/Paste, or Ctrl+V ) into your response.