The difference is not likely to be a matter of WinXP Home versus WinXP Pro, but is more likely to be due to a difference in the sound processors installed in the two machines and the setup done by the maker/seller.

The "sound card" can be a separate card that plugs into an "expansion slot," or it can be a removable "module" that plugs into a socket on the motherboard, or it can be an "integrated sound" set of components that are physically part of the motherboard. Each of these will be accompanied by the individual "controller" with its own methods of setup and "adjustment" picked by the computer maker. Controls may be in different places on different computers, but the differences are mostly due to the "sound hardware" and associated drivers in each specific computer rather than to the OS.

With a new computer, you may need to check to see whether the builder/seller installed the "wave tables" that are required to play midi, and whether they're turned on. The program that you use to create and/or play midi may also need to be set to use the same ones that the system setup is using.

WinXP should have default tables installed, but they may not necessarily be turned on (in Control Panel), or Noteworthy may be asking for different ones.

XP Pro has all of the same widgets and gadgets that were in your XP Home version, but has a whole bunch of additional stuff to make it a lot easier to maintain, manage, and, when necessary, to fix the system. You shouldn't see much difference in daily use, but if you (or your techie) should need them when things go askew, the tools are much better in Pro.

You got a different machine. It was set up differently when it arrived. It's the setup that's your problem - not the OS version.

John