The eula.rtf files are End User License Agreement files. They are stored on your drive when you install applications. The reason you cannot remove the files is that you do not have the ownership rights to the files.
To change ownership:
Right click on the parent folder of these files and right click on this folder.
Click on Security tab.
Click on Advanced button.
You will need to change the ownership using Change Ownership to your username.
Once you are the Owner of the folder and all subfolders and files, you can delete them.
Hope this helps.