Saving data before upgrading to 2.4

[Bob Plantz]

I'm running 2.3.9 on Windows 7. I downloaded gnucash-2.4.0-setup.exe.
There was a warning on the download page saying that I "should uninstall
any earlier GnuCash version...prior to installing 2.4.0." How do I
preserve all the data I've already entered into gnucash over the years?

I say "years" because I've been using gnucash on Ubuntu for several
years now. When I decided to do my financial stuff on Windows 7, I
simply copied the files from my Ubuntu installation.