
Try performing a clean uninstall and re-install the RealPlayer. To do so, please follow the below article:
https://customer.real.com/hc/en-us/articles/204040013
If you are still unable to trim, please provide the following information:
• Are you able to play those files?
• Did you receive any error message? What does it say?
• What is the file format?
• What is the operating system of your computer (Windows XP, Vista, 7, 8, 8.1, 10)?
• What version of RealTimes or RealPlayer is installed? (See https://customer.real.com/hc/en-us/articles/204039513)
• Do you have any security software installed (Norton, McAfee, AVG, etc.)?
The more specific you are, the better I will be able to assist you.