Since I came to this thread by search engine, having experienced the same problem (with the Namecoin Qt client), I will add that for anyone's future reference, on Windows 7 at least, you can just type "%appdata%" (without quotes) into the address bar of a Windows Explorer window, and it will take you there.

blogospheroid, on the off chance you read this, and have not learned this lesson in the past two years: when you find the answer to questions, it's more helpful to others if you share what the answer is, or link to it, instead of just saying "I found it".