I just lost my Wi-Fi router and ADSL modem to a lightning strike. To replace them I just bought a Belkin Surf Wireless Router and acquired a used but working ADSL modem.
The modem works great when I connect directly to it.
The Belkin seems to be working properly; the signal strength and coverage seems great. Except that all connections through it (Wi-Fi or wired) are extremely slow and unusable.
After searching around I see this is a fairly common problem. There is talk about using Google's DNS servers; this doesn't begin to help. There's talk about swapping the cable, that didn't help me either. There's talk about smaller MTUs and disabling firewalls and other random guesses. Nothing has helped me.
I can't get it to work nicely with either Linux or Vista.