Hi P R6,
Do you mean the Hyper-V feature is currently enabled on all the three machines? If you are sure the feature was not enabled when you bought them, it was supposed to be turned on by someone. This can be done remotely but the administrator privileges are required.
The work or school account is a way to enable personal devices to access work resources. You can check the work or school account here.
I recommend taking immediate steps to secure your devices and data. This includes running antivirus scans, changing your passwords, and enabling two-factor authentication on your accounts. You may also want to consider resetting your devices to their factory settings to remove any unwanted software or virtual machines.
For the BSOD issue, it is recommended to make a new post it in the Windows Client for IT Pros / Performance forum.