Cannot connect to network with WEP key encryption

The WEP encryption key is configured in the router's wireless settings.
WEP key is not as strong as the later WPA or even better WPA2 encryption keys.
To secure your wireless network from unauthorized access, please click on this link and follow my instructions :- http://www.fixya.com/support/r3559128-wireless_router_security

Network Key (WEP, WPA, WPA2 Encryption key) To connect your computer to a wireless router, you click the Refresh network list, then Choose your wireless network and then click Connect to your secured Wireless Network, it will asks for a Network Key before allowing you to connect into your wireless network. This Network Key is either the WEP, or WPA or WPA2 Encryption key that is configured in the Wireless settings in the Router. The Passphrase is an alternate way to setup the Encryption key.
When you are requested for a Network Key, you can just enter the Passphrase or WPA or WPA2 key that was used to configure the Encryption key in the wireless router. http://www.fixya.com/support/r5270415-network_password_network_address For information on securing your wireless network, configuring the wireless router and configuring the wireless card in the laptop/computer, please click on this link and follow my instructions :- http://www.fixya.com/support/r3559128-wireless_router_security

Network Key (WEP, WPA, WPA2 Encryption key)To connectyour computer to a wireless router, you click the Refresh networklist, then Choose your wireless network and then click Connectto your secured Wireless Network, it will asks for a Network Keybefore allowing you to connect into your wireless network. This NetworkKey is either the WEP, or WPA or WPA2 Encryption key that is used toconfigure the Wireless Router. The Passphrase is an alternate way tosetup the Encryption key.
When you are requested for a Network Key, you can just enter the Passphrasethat was used to configure the Encryption key in the wireless router.http://www.fixya.com/support/r5270415-network_password_network_addressFor information on securing your wireless network,configuring the wireless router and configuring the wireless card in thelaptop/computer, please click on this link and follow my instructions :-http://www.fixya.com/support/r3559128-wireless_router_security

Network Key (WEP, WPA, WPA2 Encryption key)When you clickRefresh network list, then Choose your wirelessnetwork and then click Connect to your secured Wireless Network, itwill asks for a Network Key before allowing you to connectinto your wireless network. This Network Key is either the WEP, orWPA or WPA2 Encryption key that is used to configure the Wireless Router. The Passphraseis an alternate way to setup the Encryption key.
When you are requested for a Network Key, you can just enter the Passphrasethat was used to configure the Encryption key in the wireless router.http://www.fixya.com/support/r5270415-network_password_network_addressFor information on securing your wireless network,configuring the wireless router and configuring the wireless card in thelaptop/computer, please click on this link and follow my instructions :-http://www.fixya.com/support/r3559128-wireless_router_security

The windows wep key is something that is normally set up when you configure your router. It is something you yourself add when you want to encrypt your network. Here is a good guide for doing that:
http://www.tekstenuitleg.net/en/articles/networking/wireless-security-guide/configure-wep.html

Note that there are different levels of encryption you can use. Wep is only one of them.

you can find this out by connecting to your linksys router with a cat 5 cable.
in your browser such as internet explorer or firefox type
192.168.1.1
login with your login/pass that you assigned to it.
go to the wireless tab and go to security
it will show the the WEP key that is needed in order for your laptop or wireless devices to connect.
BTW I would recommended using WPA as WEP is not secured.

Configuring WEP:

1. Use an ethernet cable to connect a computer to any one of the four LAN ports of the NETGEAR router.
2. In a web browser, enter the router's IP address - either http://192.168.0.1 or http://192.168.1.1 by default.
3. When prompted for a Username and Password, enter the default username and password (admin; password) unless you have already changed it. NETGEAR recommends changing the default password to increase the security of your network.
4. Select Wireless Settings from the Setup menu in the left-hand navigation bar.
5. Under Security Options, select WEP (Wired Equivalent Privacy).
6. From Security Encryption (WEP) > Authentication Type, select Automatic.
7. From Security Encryption (WEP) > Encryption Strength, select 64-bit or 128-bit. NOTE: You will need to configure your wireless computers with the same setting.
8. From Security Encryption (WEP) Key, select Key 1 and enter a key.
9. • Note: WEP keys are entered in hexadecimal digits, which are any combination of 0-9, A-F.
   • • If you selected 64-bit under Security Encryption (WEP) > Encryption Strength, then enter 10 hexadecimal digits for your key.
     • If you selected 128-bit under Security Encryption (WEP) > Encryption Strength, then enter 26 hexadecimal digits for your key.
   • SAVE or KEEP NOTE of these values - they will be required to connect wirelessly to your network.
10. Click Apply to save the settings.

The WEP encryption key (network key) is in your wireless router, without this key the wireless router won't allow the computer or laptop to connect to this wireless router.
I recommend you use WPA or WPA2 encryption, it is much stronger than WEP.
The WEP, WPA, WPA2 encryption key is in your router's wireless settings. Log into your router and got to the wireless settings, you will need to get the SSID and the encryption key. Then go to your computer or laptop's wireless card and configure it with the router's SSID and encryption key, so it will then connect to the wireless router and the Internet.

To secure your wireless network from unauthorized access,please click on this link and follow my instructions :-http://www.fixya.com/support/r3559128-wireless_router_security.

If you select WPA security mode then you can not add the network manually.
I think the OS on your computer is windows XP.
You can connect to the netwoek using the windws utility.
If you select WEP, then you can add the network manually.

Click here for more information about router and networking

Sir,

Under 'preffered networks', which can be found on the Wireless networls TAB in advanced settings, you will see your network there. Click on it and then hit properties. Under the 'Association' TAB, you will see network authentication, choose WPA-PSK or WPA, but I will imagine that your key is a Pre-shared key. Enter it there. Data encryption will be TKIP and not AES. Go to connection TAB, and make sure the box is checked in that section. If these steps fail, then you can always change your encryption to WEP. You can do this using a computer which connects to your internet through the WPA key. Once connected on that PC, open up command prompy using the command cmd in the RUN box when you click on the START TAB. A black box will open, simply type ipconfig and look for "default gateway"...it will have a number with a few dots, like this one: 192.168.1.254.....etc. Enter this code into your internet browser search bar, and hit enter. Your internet providers interface will show up, you can find a tab which will have something to do with wireless security, and there you can change the WPA to WEP, with a WEP key of your choice. If you are prompted for a password then you should know it! Sometimes, the usernames can be simply 'admin'. If you manage to change your security to WEP, you can use your laptop!

All the best.