You have two paths you can take.
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The FTDI serial converter chip used on your board has a USB drive but it is 'unsigned' and you can't install it without going through a sequence of manual windows hoops to allow you to install such an unsigned driver, however the driver is included in your Arduino IDE distribution files. A goggle search on "installing unsigned drivers in Windows 8.1" should find several sources for the gory details. This probably not the best path to take as there are newer device drivers available as told in #2.
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The FTDI site has official 'signed drivers' that can be installed in your Windows 8.1. The trick is figuring which driver you need to support the FT232R chip your Duemilanove. I think this is the correct driver selection page for your board:
VCP Drivers - FTDI