John, I now have 13GB of free space on the HD, and that defragged. When I defragged, most of the space looked contiguous.
This was a W98SE computer until MS stopped supporting it. There is only one HD in there, the other connection is still to a Zip drive until I'm sure I won't need it any more. I do have a portable 500GB HD which only has some music in it, yet. That also wouldn't open, but an unplug-and-replug fixed it. USB connection.
The computer has worked well since XP went in, with 512MB of RAM. Boot isn't bad. Outlook Express, which since the problem is the worst offender, works fine when it is open. I can sometimes ginger up the opening by clicking something else, such as the Opera browser I use, and then OE opens a little quicker, and at the same time as Opera. A little quicker is relative, like four times as long as it should take.
I take your point about larger HDs, but I'll have to wait a while, because the chancellor, Her Indoors, bought me the portable HD. I'll keep my eye open for a cheap larger internal HD and swap them over, which will mean a full install.
Gargoyle, my relatively important files are on a thumbdrive and hard copy, because they are business files. Apart from that, only a few photos are irreplaceable. I rarely have more than two programs open at one time. One .dll file did go missing, an unimportant program.
I uninstalled it. I didn't defrag in Safe Mode, never have, didn't know you could. One lives and learns.   ZoneAlarm. I'm still using the old version because the update wants me to REMOVE my viruskiller to install. I thought that I'd wait until the viruskiller was due for resubscribing and then buy their(CA's)firewall. Perhaps I should.
I definitely should have a boot disk, obviously. I've never had the need of one with W98SE or XP, but XP not being able to overinstall caught me by surprise.
I'll look at the rest of your suggestions tomorrow. 8.30pm here, and once again I've had enough of computers. Thanks for the help, guys and 'I'll be baaaack.'   Chris.