1. Your wireless settings don't match between the router and your laptop
You look to be using WEP. Is there a way to look at the settings on the router? There are two different key lengths for wep: 40/64 and 128. If the key doesn't match *exactly* you won't connect. Make sure the key is the correct length. Normally you shouldn't be able to enter a wrong length.
Does the wireless card "connect" but no internet access?
2. It's possible the wireless portion of the router isn't compatible with your new laptop. Respond back with the make and model of the router and we can take a look.
aem: We meet again! Just while I'm typing!
BTW: Actually Windows 7 *is* compatible with WEP. If you look at the drop down you'll see "Shared". That's actually one type of WEP. There are two kinds of WEP: Shared and Open (Not the Open No Auth type). Some older gear only supports one type instead of both. If they don't match, no connect. The thing about WEP is it's not OS dependent. WEP is down in hardware on the adapter. Not in on the driver
If his router is too old it may only support Open WEP. If his new laptop's wireless card only supports Shared WEP, then it won't work.
But you and iseeuu suggesting to use WPA or WPA2is spot on. WPA is easier to configure and more secure anyway. WPA2 is even better.