When any web browser connects to a remote web server it presents its User Agent string. The user agent string gives information about the browser and operating system. This information winds up in the web servers access log. If you have a firewall at work with a proxy server for web browsing, the user agent string is used to determine if your browser is an approved version. An example:
Mozilla/4.0 (compatible; MSIE 5.5; Windows NT 4.0)
The following registry hack lets you control the User Agent string.

Hive: HKEY_LOCAL_MACHINE
Key: SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\User Agent\Post Platform
Type: REG_SZ

The Post Platform key may have several values. These values make up the user agent string. To prevent this info from being spread around the Internet, delete the values under this key.