This is caused by an issue with Windows Media Player© 11 on Windows Vista© when using unsigned Audio DSP or Other DSP plugins. To fix the issue, you will need to disable all Audio DSP and Other DSP Plugins currently enabled in Windows Media Player before converting any files with MuvAudio.  Please follow these steps to fix this issue:

1. Open Windows Media Player.
2. Hit the Alt key on your keyboard to bring up the old-style menu.
3. Click on Tools.
4. Click on Plug-ins.
5. Click on Options.
6. Under the Category heading, click on Audio DSP.
7. Under Audio DSP, make sure all plugins are not checked. If they are currently checked, please uncheck them.
8. Click Apply.
9. Next, under the Category heading, click on Other DSP.
10. Under Other DSP, make sure all plugins are not checked. If they are currently checked, please uncheck them.
11. Click Apply.
12. Click OK.
13. Close Windows Media Player.
14. Restart your computer.
15. You should no longer get the message to restart your computer unless you install a plugin that is not signed. If this happens, just follow these steps again to resolve the problem.