This error is due to a conflict with OMEI Backupper.
As a workaround, you can follow these instructions to resolve the issue.
- Right click on My PC
- Click on Properties (This should open System Properties)
- Click on the Advanced tab and click Environment Variables button
- Under System Variables, select the "Path" and click Edit.
- In the Edit environment variable, select the line where you see "AOMEI Backupper" and Delete it.
- OK to close this window
- Restart your PC and try to use RealPlayer again