In order to test if wireless adapter in win7 laptop works well with modem router, you can configure open network (no wireless encryption) on modem router temporary, after that connect to it with your laptop.
If it works, probably you did not configure wireless encryption correctly on modem router or laptop.
If you need more ideas, take a look on this wireless network troubleshooting tips article.
Hope this helps.
Wireless Problems Unable to connect to WIFI on Windows 7, TM-DLINK DSL-2640B wifi modem router