How to find the WEP key for linksys wrt600n router ?

If you are using a WEP on your router, then you SET IT. You have to Log into your router to get into the setup. Then go to a Wireless Security section. A password/key that you picked is RIGHT THERE.

Best of luck and I must say Happy Computing!The routers ship with default the passwords to access the setup options. you can find the info for your router here..

phenoelit-us.org/dpl/ website

You will then have to go inside and then check for your wep key..

If you have lost it and now you can't connect you will have to reset the router by pressing the reset button, usually on the back or the bottom of the router and logging in with the default info from website above

You need to log in to your router. You can even do this using an internet browser. Firs of all t, find out the ip address for your router and type it into the address bar of your browser (maybe the web search or go right to the linksys site). It is typically something like:
192.168.1.1
192.168.2.1
192.168.0.1
10.10.10.1

You will most likely to be asked for a user id and password. Now Try the defaults (again, you should be able to find this online or in your documentation). Once you are logged in, go to the wireless configuration and navigate to the WEP setting. It should definitely be listed there.