My PC is getting on in years, and I've maxed out the allowable upgrades to the motherboard. It limps along well enough. Using Windows XP home edition, 2.0 MB RAM Dell Inspirion 2400. Considered Old School these days, but we're kinda attached.
I periodically use the system tools Disk Cleaner and Disk Defragmenter, and use AVG Free 8.5 to regularly scan and remove malware, etc.
There are tools to clean up the registry, start up menu and other things like that but I'm anxious about unintended consequences of using them.
My question, what kinds of upkeep do folks recommend to keep older systems near peak performance that are either free or relatively low cost?