XP Diagnostics

Is there a program that will diagnose XP and find errors?

 

OLDSALTY--Rule #1. If it works, do not fix it.
Rule #2. If you have a specific problem, give us the details and we will try to help.
Rule #3. Your question is very broad (errors in the Registry, Icons, BSOD, error messages, running slow, etc.). Go back to Rule #2.
Of course none of these Rules means you should not do maintenance every now and then. Delete cache (Temporary Internet Files), delete History, delete Temp files, run ScanDisk, perhaps Disk Defragmenter, reboot (if you do not do this every day, anyway), etc. And that you go to Windows Update from time to time.
I assume you have antivirus, firewall, spyware detectors, Spyware Blaster, etc. installed (and where appropriate, kept up to date).
If you are looking for trouble see the Similar Threads at the bottom. There are other general diagnostic programs, but see Rule #1.