The USB to RS232 adapters are notoriously choosy and any particular adapter will work with one setup and not another.
You should try your adapter to see if it will work in your setup (if it does not work you will not know where to place the blame).
If it fails to work you must choose either to get a cheap PC with an RS232 port - speed is relatively unimportant - or post details of your setup and see if anyone with a similar setup can give you details of an adapter they use successfully.
basically yes mate i had the same set up as my computer is new..flashed my box a hundred times this way.
just make sure you install drivers it should have come with disc.