This problem may be caused by several problems like a corrupted user account. To solve this, you can try several things. You can turn on/off your UAC(User Account Control). For more info about this matter try visiting the following webpage 1 and webpage 2.
Also, you can try to create a new User Account on your computer and try installing/running this application from there. To create a new User Account you can try going to Start -> Control Panel -> User Account -> Create a new user account and follow the instruction provided from there.
You can also try running the application using Administrator Wrights. To do that, you can try going to the folder where you installed the application (ex: C:/Program Files/.../LOTRO/ ) right click on the .exe file and choose Run as Administrator.