ssc install panels
checking panels consistency and verifying not already installed...

the following files already exist and are different:
    C:\stata\stata13\stata13MP\ado\plus\p\panels.ado
    C:\stata\stata13\stata13MP\ado\plus\p\panels.hlp

no files installed or copied
(no action taken)
r(602);
我想安装panels这个命令，但是出现上面的提示，有大神知道是什么意思吗

Here's one solution found online.

1. Find the package of previous version by typing: ado, find(table1)

2. If that command returns a result, you can uninstall any of the versions that you may have installed on your system with: ado uninstall [#]
Where you'll replace the # character with the numeric value returned from the first command. In the case that you have multiple versions of the same package installed, it might be good to uninstall each of the versions and then try to use the command to install from SSC.

非常感谢