具体的操作步骤如下：
步骤一：打开Beyond Compare软件，点击上方的“工具”菜单，选择“选项”命令
步骤二：左侧选择“启动”栏目，右侧勾选“在资源管理器环境菜单中包含Beyond Compare”，并在“比较”命令右边位置点击下拉按钮，选择主菜单
点击确定就OK了。
测试：（注意：如果不好使请看最后）
选择一个或多个文件可看到效果
如果还是不好使，可以参照官网解决办法
https://www.scootersoftware.com/support.php?zz=kb_shellex
SHELL EXTENSION NOT DISPLAYED
If the shell extension is checked in the options dialog but it isn't displayed in Windows Explorer's right-click menu, applying registry patches will often fix the problem.
Beyond Compare 4 registry patch: BC4ShellExFix.zip
Beyond Compare 3 registry patch: BC3ShellExFix.zip
To apply the registry patches:
- Uninstall Beyond Compare.
- Download the registry patch zip file that matches your Beyond Compare version and unzip it.
- Double click on Remove.reg to remove Beyond Compare's shell extension registry entries.
- Reboot.
- Install Beyond Compare 3.3.13 or the current version of Beyond Compare 4.
- If Beyond Compare is installed to a location other than the default folder (C:\Program Files\Beyond Compare 4), edit the installation path in Add_64-bit.reg or Add_32-bit.reg.
- Double click on Add_64-bit.reg or Add_32-bit.reg to add Beyond Compare's shell extension registry entries. Use patch that matches the architecture (32-bit or 64-bit) of your operating system.
- Reboot.
翻译过来就是：（但是并不需要这么麻烦，直接执行步骤2，3，6应该就可以了）
- 卸载BCompare
- 下载对应BCxShellExFix.zip，并解压
- 双击Remove.reg来移除BCompare的右键扩展功能菜单；
- 重启电脑
- 重新安装BCompare
- 根据电脑的位数选择脚本：Add_32-bit.reg，Add_64-bit.reg。如果修改了BCompare的默认安装路径，则需要修改对应脚本中涉及到的BCompare路径
- 再执行一次步骤6
- 重启电脑