It seems strange in this day and age that anyone would want to use an outdated serial connection to their computer. Not many machines have them now so what do you do if a device you need to connect is serial? Buy one of these leads and the job is done. The only (very minor) problem you may have if you are not to clued up on serial connectors is that once you have this lead between your computer and the serial plug on your device, it will still be seen by a lot of software as a serial connection.
With USB, you can simply plug it in any port and away you go. With serial, you have to select, usually from a drop-down list, which COM Port (Communications Port) you are using. The worst that this can be is that you select each option in turn until it works, probably no more than three guesses, and that is it. Once you have done this, the software will store the info and it will connect each time from then.
I use this to connect my Garmin eTrex H Handheld GPS Navigator
GPS to both my iMac and XP based Netbook. Works perfectly and is a very well made product that will offer years of service to come. My local high street electronics shop wanted £24.99 for virtually the same thing!!!!!