I've been meaning to ask about this. I found a file called grub.cfg,
which appears to be the replacement for menu.lst The comments in the
file say that it shouldn't be edited, but I did after backing-up the
original file. It still seems to work OK.

I've changed the delay time, changed some of the text it displays, and
deleted some unwanted entries, by removing the stuff between { ... }.
I've also checked that the default operating system can be changed, if
required.

Is there a better way to make these changes?