There is at least one other general maintenance task that may help speed up
this older computer. Run the Microsoft system configuration program,
msconfig (Start - Run - msconfig). Go to the "Startup" tab, and uncheck as
many startup programs as you dare. It's not unusually to find 20 or 30
programs checked, and some of these programs can cause things to slow down.
I've got my own system down to two to four programs in the startup group.
Obviously, you don't want to disable your virus checker, but you may find
that many of the checked items are not needed to run the PC.

Alan