There are some free tools which allow you to monitor connectivity between a central test box and the router at the customer end.
If you had one of those you wouldn't be hampered by "thinking different" and you wouldn't need a Window box either.
If you had one of those it *might* show if there were connectivity problems (e.g. packet loss) between your router and your ISP.
Where can you get such a tool?
Try
http://www.thinkbroadband.com/ping
You can do this ping test stuff at the same time as the other suggested stuff wrt checking your wireless connectivity. I've tried InSSIDer but couldn't find an SNR indicator only a signal level indicator. Netstumbler used to have both signal strength and SNR. A high signal level is not much use if there is another high level signal on the same channel, causing poor SNR.
Also on similar lines I'm not sure how InSSIDer handles non WiFi devices in the relevant bands - e.g. if someone has a video sender on the same frequency as your WiFi it won't affect your received signal level but will affect the signal quality; Netstumbler could show this as poor SNR, but can InSSIDer show it at all?
Put more briefly: try using different channels for your WiFi and see if it helps.