I used to LOVE that feature in Windows XP!
Just right-clicked on the WiFi icon on the Taskbar (lower right-hand corner), then Repair. It doesn't take that long, and it usually helped me since I constantly go back and forth between LAN at work, VPN on WiFi from work and home, and also VPN to my own personal server. Even if you didn't need to refresh, doing so never hurts!
Unfortunately, the feature seems to be removed from Win7 :( Now you can check for problems, but it only does the refresh if it thinks it needs too, and the whole process tasks so darn long!
Is there a way to Repair my WiFi connection quickly and easily on Win7?