If you want to increase your wireless card's signal strength, you can try compiling your own driver/module rather than use the one that comes with your distributions kernel (which is in /lib/modules/uname -r/kernel/drivers/net/wireless, and will be called ipw2200.ko for ipw2200). Because you have a Dell, I'm betting you have an Intel PRO 2200BG wireless card. The TX-Power (transmission power) is pre-set at 20 in the Linux driver, not sure about Windows, but I have a feeling it's the same.
Because I'm a hacker, and I do digital forensics, I compiled my own driver/module and jacked up the TX-Power for ease of tapping into wireless networks off the street. How to do this? just look for "Jo Shmo's" post in the thread link below: