Every time you modify a theme, Windows 7 will save your modified theme as an unsaved theme. This is normal and not a bug. However, if this happens without editing the theme on startup, you might want to read about a few common issues here.
Try saving your unsaved theme as a new theme (right-click, save) and see if your theme keeps changing back to an unsaved theme. If it does, there is something modifying your theme or your theme might even be corrupt.
As reported here, if your Windows 7 theme keeps changing it’s very often a 3rd-party tool that is causing this! Try to disable all desktop goodies like virtual desktops or other applications related to Windows 7 themes and wallpapers.
1. Disabling Aero can cause problems. Also make sure that you have the latest graphic drivers!
2. StepAnother issue might be 3rd-party tools that modify your desktop and cause your theme to appear as an unsaved theme. BGInfo, one of the SysInternals tools that you can use to display your IP address or MAC address on your desktop, is known as a problematic program.
- DISABLE: Multidesk, Acer Ferrari Wallpaper, BGInfo and all tools that modify your desktop.
3. StepTry to create a new user account and see if the problems persists.