Just an update. Dorothy did indeed sort me out - in fact, all I needed to do was to back up my file, then import the .sqz file (actually, I guess I'd better check for any others on my old hard drive as well...) to my new computer. After a few minutes when it thought everyone on the picklist was number 186, which had me worried, it settled down and all seems fine.
Now I just have to catch up on 12 years and four versions worth of updated features... wish me luck!
Many thanks, Jim and Dorothy!
Adrian