Yes, several USB to Serial adapters will work. In fact I haven't found one yet that won't work. Note that there is no guarantee that all programs will work with all adapters. I've had very good luck with adapters using the FTDI chip set.
You can use FTDI or Prolific. Those are the 2 major chipsets the USB1 (unidens usb plug) is a prolific chipset. You can get one of these and it will work just fine.
Xeno194 what if I'm running windows vista will it work I was looking at the system requirements and it has Supported OS: Windows 98SE/ ME/ 2000/ XP.....
Yes the trendnet will work and so will the one that Hiegtx linked you to. Which ever one you choose make sure you download and install the latest drivers before you plug in the cable. I have used the trendnet without any issues at all.