I would steer well clear of the ebay and standard ones in consumer electronics stores. Many won't work. I never got a Belkin one to work that I have.
I use the Aten one to connect my Losmandy GM8 to my Vista laptop.
Threads like this one will be useful to you:
http://www.iceinspace.com.au/forum/s...ad.php?t=36816
Using Vista I have found things work quite well providing I keep the configuration of USB hubs and converter in the same arrangement. That is, the USB 2 Serial converter plugged in to the same port on the USB hub and the USB hub plugged in to the same port on the laptop. That way the serial port number stays the same and Vista doesn't have a problem recognising it without a reboot being required. Realising this has made my life much easier.
In my observatory my PC has 4 ports via expansion cards.
Roger.