from vista onwards I don't think the 15pin d-connector gameports are no longer supported, if its a sidewinder 3d force feedback pro joystick then you will have to build a 3dp-vert interface to use it (http://grendel.koolbear.com/3dpro.htm),
standard usb to gameport dongles are not compatible.
This is only for the 3d force feedback?
If I use a standard adapter with the Sidewinder Precision Pro, will it work alright?http://www.amazon.com/Microsoft-Sidewinder-Precision-Pro-Joystick/dp/B00000JDFT/ref=cm_cr_pr_product_top/175-6183593-5288943
E: I did some digging around, and it looks like the Sidewinder Precision Pro with the part number X03-57540 (mine) are compatible with a standard USB adapter, they have the converter built into the joystick. Thanks for your help.