I am guessing, but I wonder if you even need to upgrade! The important thing is to install the correct drivers (instructions to the computer)so that it all works for you.
What system are you using at the moment. Is it Windows 98SE, or Windows ME?......... If it is either of these you may be able to find drivers on the net which will work for you. Try putting ipod and your OS into Google and see what is there.
If you still have to upgrade, then there are good reasons to be sure your computer can run the new system, so post as much detail of your version of Windows, its RAM and Hard Disk size so that others can join in with sound advice.