Strange, it sounds like you are doing everything right but my understanding is the iPod displays the computer name, not the account, and there is no way to specify a particular user account. As the previous poster mentioned, it should sync with whatever account is logged in and running iTunes, and log out of all other accounts (as a test).
An easy test for this would be to rename your computer per the posted link, reboot, sync with iTunes via a cable, and see if the new name shows up on the iPod. Then change it back.
I'm running Windows 7. The computer name is HOOD (a nearby mountain). The administrator account I created is ADMIN. There is also a user account called USER. I'm logged in and running iTunes as ADMIN and the iPhone displays the computer HOOD.
I assume you enabled wifi sync in iTunes and then synced the iPod at least once. I would turn off Vista's firewall and any security suite firewalls installed (McAfee, Norton, AOL, etc.). If that makes you nervous (and it should
) unplug your router from the Internet while your security is disabled.