tedster - 5:23 am on May 5, 2010 (gmt 0) [edited by: tedster at 5:26 am (utc) on May 5, 2010]
We have a dedicated IIS forum [webmasterworld.com] where you might get some in-depth technical help - it;s not really a Google topic. As a top view, the server must first be configured to create the log files. And then there are a few options that can be important - such as recording the referer string and not just the request, user agent and IP address.
However, googlebot won't send a referer, so it wouldn't matter if this is the only reason you want to use it. However, you certainly need to look at the IP address - there are lots of rogue bots that spoof the googlebot user agent string [webmasterworld.com].
[edited by: tedster at 5:26 am (utc) on May 5, 2010]