This error is due to a conflict with OMEI Backupper.

As a workaround, you can follow these instructions to resolve the issue.

1. Right click on My PC
2. Click on Properties (This should open System Properties)
3. Click on the Advanced tab and click Environment Variables button
4. Under System Variables, select the "Path" and click Edit.
5. In the Edit environment variable, select the line where you see "AOMEI Backupper" and Delete it.
6. OK to close this window
7. Restart your PC and try to use RealPlayer again