"CableNut 4.08 will appeal to experts who already know their TCP/IP settings: It provides tweakable TCP options in text boxes with little or no explanation. It has preconfigured settings for cable, DSL, and dial-up on Windows 9x and 2000, but doesn't seem to work with Windows XP. CableNut does not perform tests, so if you make any changes to your connection, you'll have to look elsewhere to confirm that they tweaked your connection for the better."
From a PC Magazine review
"Is it worth installing?" Doubt it - it will be the first one of these that is worth it.