Does Win XP get old and tired?

Windows accumulates a lot of garbage, .e.g., old files or registry entries over time. For instance when you delete a program there are always some files and registry entries that aren't needed and aren't deleted. Free programs like CCleaner and Eusing Free Registry Clearer will clean some of this stuff out and running them regularly helps. Also Defragging will help. After 3 plus years the best thing you could do is a clean install of Windows with a full format but you'll lose everything on the drive so you have to back up all your data.

format is not always the answer, cleaning out the prefetch, regular defrags of the entire pf, and file system, increase MFT size, and cluster size.
disable some services, create back ups of registry, use a registry monitor with restore features for install programs that have been uninstalled.
Create startup scripts and shut down scripts to remove dll and prefetch, temps, create bat file for memory CPU services.
all these things will prevent any system from slowness caused from clutter . Myself I have created a long list of reg tweaks in one file so it can be imported or merged.