Ever hear of the MTU? Nope, it's not the Boston subway or the music video channel. It's an obscure setting in Windows 95's Registry, known mostly to people who use pocket protectors.

But don't let that put you off. Tweaking the MTU (Maximum Transmission Unit) can double--and in some cases even triple--the throughput of your Internet access in less than five minutes. And for an unbelievable price: free.

How does it work? Prepare for a little geekspeak. Data shoots across the Internet and into your computer in packets. The packets are sized for optimal transfer speed over Internet backbones, routers, and ethernet networks. But if you're connected through a modem and an Internet service provider, this default packet size is less than optimal. The result? A substantial performance hit because the packets are fragmented and need to be reassembled.

Naturally, I'm going to point my finger at Microsoft. The computer giant obviously wasn't paying attention when it set the MTU default to 1500 in the Windows 95 Registry. Lower that number to 576, and your throughput will increase substantially. This MTU fix is almost as good as squirting some WD-40 into the back of your modem. (PC World's lawyers warned me to say I was just kidding about the WD-40. Kids, please don't try this at home.) Even Microsoft has admitted that the change is useful and has repaired the problem in Windows 98.

Don't doubt that changing the MTU makes a huge--no, humongous--difference. In a Bass Laboratory blind study, I changed the setting on my wife's system without telling her. Touching her machine is risky (fortunately, I'm insured against spousal computing disasters), but this particular death-defying act paid off. She asked if I had changed ISPs or had done something to her machine, because her favorite Internet sites seemed to be--and I quote--"coming on-screen lots quicker than usual." Ta-da!