I have Mega and Nano boards. While on Win7 I can use both and everything works fine, on all my various WinXP only Mega works fine. Nano always comes up with installation issue: "USB2.0-Serial" does not have proper drivers - question mark in Device manager. I have tried MANY drivers (from original Adruino package, from FTDI page, many older versions, searched Google for hours and trying a lot), no success at all.
This is perhaps WinXP (tried on more versions, both Pack2 and Pack3) issue with installing virtual COM port for Nano (while Mega works perfectly). Please advice me what and how to install on WinXP to be able to use Nano as well.
Since this thread is still one of the top Google hits for this problem, I figure I would add this:
I had the same problem trying to install the driver for an Arduino Nano on Windows XP. I tried pretty much everything, but only this worked: https://arduino-info.wikispaces.com/Nano-USB-Drivers
Probably, you have Chinese Nano with CH340 USB/serial converter, according the link you've posted.
Previous discussion is about FTDI FT232RL chip as genuine Nano has. It is different and same about driver. It has nothing with the XP directly.