'leenia, you've been using NoteWorthy Composer for years..'

Yes, that's part of the problem. I don't remember whether my computer has an unusual sound card. (It used to.) The company which put out my keyboard is out of business. I do know that I had to make a special request for a MIDI port the last time my computer was upgraded so I could keep using my piano keyboard.

Evidently the young guy at the shop didn't know there is such a thing as a MIDI-to-USB cable. In fact, one reason I am posting here is that the young guys at the shop don't know anything about writign music. To them, music is something you download and play on your ipod.

So thanks for the link, IvanB. Your page contained an ad for a 25-key synthesizer which costs $179 plus shipping. It has a USB cable and works with XP and above. It looks like it would do nicely for music editing.

By 'music editing' I mean things like:

change the key
write a new part
change treble to bass and vice versa
change the time signature
remove poorly-conceived special endings
convert a tenor part to a descant

These are things I do all the time.