Updated Download Link 05/09/2015 !!!
If you have this wonderful pci wireless card and you switched to any Windows 64 bits edition (XP/VISTA/7/8), you probably have to install this card driver again.
Actually it was no easy job for me to find it in the web back when it happened to me.
As it cost me some time to find it, I'll save you that time.
This driver also works for the 32 bits editions.
The 64 driver version was not hosted in Cnet.com site. So I emailed the chipset manufacturer Ralink and after a week they replied with this link. They told me that the driver I needed was the one for the "RT2561ST" chipset.
RALINKTECH.COM Download Driver CWP-854 32/64 bits Windows (2000/xp/vista/7/8)
Download Driver updated 14/04/2015
password so you can uncompress it : hongouru.blogspot.com