Mostly we save the wireless key of our network on our computer when connecting to one.
If you faced the situation when you have forgotton your wireless network key but luckily had saved it on your computer while connecting to the wireless network last time on windows(xp), then to reveal / retrieve it back you dont need to reset your router.
There are various utilities available out there for this purpose, but one of them that i used personally and found to be useful is Wireless Key View.
Link to the official site is:
By this simple file you can easily show/reveal the saved password for wireless network saved on windows xp in a very small time.
Basically the password for wireless key is saved in the windows registry and can be easily shown/retrieved/revealed by a software like this which can read the registry values saved for this wireless key and decrypt them and show it to the user.