Does XP Help Center phone home?
 

Left the laptop idle; found it with CPU at 100% and HDD busy. Opened up Process Explorer; found the Help Center service had started up and was very active. I hadn't used the Help Center all day.

Was it talking to Microsoft HQ? There's no entry for auto-updating in its options.

I found an updates log in the relevant folder on C. Last one was in 2004.

Any ideas?

You can check which components of Windows call home with your firewall (you DO have a firewall?). Just set it to ask on all applications and system services - it will tell you straight away when anything tries to call out.

Thanks Sallyann1234.

I use Comodo Firewall Pro. I've set it to block any call out attempts by the Help Center service.