A long llst of free MS orietated XP related programs are seen at http://bhandler.spaces.live.com/blog/cns!70F64BC910C9F7F3!1231.entry Some of those under the troubleshooting and utilities section are for different types of diagnostics. Everest home edition was one that was popular when a free version was available.
If you also want a system information tool that will provide an excellent breakdown on the system, hardwares, softwares, and operating systems as well as even temps the SIW is a small freeware found at http://www.gtopala.com/siw_on_pc_world.html
It will scan the hardware for obvious faults I have yet to see it fail a mobo or processor yet, but I have seen it fail drives and RAM. Then again if you had a bad mobo or processor you probably couldn't even run PC Check.