I have been able to run 'java' okay. There is no 'javac.exe' in the
\bin directory. I've set 'JAVA_HOME' and 'PATH' via 'Environment
Variables'.

(I should explain that a five hours in XP has me in a pretty anxious
state -- I normally use Linux. But that's hardly an explanation of this
madness.)

Thanks,

Jon C.

[...]

Apologies for the delay in following up -- Windows suggested that it
clear some space on the C: partition; I agreed, not realising that the
task would take more than one hour. I was installing JDK onto another
partition, but maybe the shortage of space on C: is a clue to the odd
behaviour descibed.

In any case, the reinstallation (from the /same/ .exe file) worked and
everything is as expected; 'javac.exe' is now in 'jdk...\bin'.

So, there are things in 'jdk...\bin' that were absent earlier, e.g.
'javac.exe'. And 'tools.jar' is in 'jdk...\lib' -- also absent earlier.

And there are files missing from 'jdk...\' that were present earlier --
I've forgotten the details, but a bunch of files with names suggestive
of foreign languages.

The 'pretty vague menu' (asking what needs to be installed -- jdk, jre,
etc.) mentioned above is now clear enough; initially, the method and
indication of selection was incomprehensible to me.

The other difference with the second installation is that it asked
about registering with both installed browsers (IE and Firefox), wheras
the original asked only about IE.

So, the original installation must somehow have got confused -- perhaps
by the lack of space on C:.

Thanks everyone. But probably not the last you have heard from me :-)

Jon C.