The best 'bang for buck'would be more ram. At least another 128Mb. You'll really notice the difference.
The proceesor speed is OK for what you use it for. A format (if not done already) will clear out all the bits left that are clogging up the drive.
The User Account idea won't make any difference, it's ulimately all down to the RAM.
For e.g , my old work laptop took 45mins to fully load up one day and it turned out to be a strip of RAM had come loose droppping down to 16Mb!!