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.