Basically, install/run Update for Windows XP (KB967715).
Then, for XP Home, type Regedit, and double-click on HKEY_CURRENT_USER
\NoDriveTypeAutoRun and make it 'ff'.
That will disable everything.
One note of caution:
If the Knowledge base says HKEY_LOCAL_MACHINE only, and doesn't mention
HKEY_CURRENT_USER, still check for HKEY_CURRENT_USER. With some systems
Microsoft neglects to mention HKEY_CURRENT_USER, and it actually takes
precedence over the other, so if you turn only HKEY_LOCAL_MACHINE off,
you may not, in fact, have disabled Autorun.