The device appears on the desktop but has a cross through it

Does mean that is not connected.
Double click on the icon, select your network and click connect.

If you were been connected before, you have some problem connectivity.
you can fin some help here:

1) Your Network or DSL router may have bad or missing information. Powercycle your router and/or rebuild the configuration in your router.

2) Double-check your cabling to the computer. Make sure you have the correct type of cabling, straight-through CAT 5 or possibly a crossover cable and try another cable or test the cable to make sure its working properly.

3) Check your network card to make sure its configured correctly and working properly. Many times setting the network card to 10Mbps/Full Duplex will solve this issue. To do this, open Control Panel, System, Device Manager. Go to the properties of the Network card, click on the Advanced tab and find the Link Speed and Duplex section. Change it from Auto Detect to 10Mbps/Full Duplex.

4) Check and test your firewall. Your firewall, especially if its a software firewall like ZoneAlarm, Black Ice, Norton Firewall or something else could be blocking the connection. Disable your firewall and test the connection. You may have to resolve the problem by even uninstalling and reinstalling the firewall.

5) Check your IP address assignments and workgroup settings in the computer for accuracy. Statically assign IPs to the computers in your network.

6) Reset your TCP/IP stack by downloading and running WinsockXPFix.exe a Visual Basic program designed to fix corrupted TCP/IP issues, host file problems and a variety of other connectivity issues.