Previous versions of Windows, starting with Vista and Windows Server 2008, did indeed include User Experience changes once the trial period had passed:
If Windows has not been properly activated and is not within its activation grace period, the computer is in the notifications state with the following UX:
- Upon logon, Windows displays a dialog box reminding the user that Windows must be activated. It includes options for activating now or later. If the user does not interact with this dialog box within two minutes, the dialog box closes, and the logon process continues normally.
- In the notifications state, Windows changes the desktop wallpaper to a solid black background, displays taskbar balloon notifications indicating the activation status, and displays dialog boxes showing what action the user needs to take.
- In the notifications state, the computer has the full functionality of the installed version of Windows, except that the following features are disabled:
- A computer configured as a KMS host will respond to KMS client requests with an error stating that KMS has not been activated.
- Windows Update only allows security and critical updates—not optional updates
- Optional downloads requiring online Windows Genuine Advantage (WGA) validation—also called genuine-gated downloads—are not available.
It goes on to point out:
the desktop still changes the background to a solid, plain black. The user can reset the desktop background to wallpaper or other background color, but every 60 minutes, Windows resets it to black and displays the notification balloon
So the behaviour your friend is seeing is not because of a virus or malware as others have stated, but a consequence of running the software outside of it's grace period.
I believe Windows 8 in the "Notification State" will show an activation nag watermark and limit access to much of the "personalisation" features.