My pc broke and my son fixed at his home. When I brought it home, I have trouble to enter network security key. My wife and I each has his/her pc. So they key must store in her pc also. Tell me how I can look it up. Thanks
Assuming this is a Wifi network security key for your router at home:
I you haven't changed it then and it is still at the factory defualt then this will likely be printed on the router somewhere, or maybe in the original packaging or manual, so take a look.
If you have changed it from the default then you could try logging on to your router from your wifes computer. Some router configuration pages will show the security key in plain text, although you will probably need to know your router admin password to get that far.
Other option is to plug your PC into the router by ethernet removing the need for the security key. From there you could change the key to something you can remember (again you'll probably need the admin password for the router).