|Can't say for sure but some hp's are not standard. See that the color's of the wires on the 20 match standard colors. I think one is a 3.3 vdc instead of 5vdc or something like that|
Anyway be sure you reset/clear bios and try again. Dunno what it might have been set to.
"Best Practices", Event viewer, host file, perfmon, antivirus, anti-spyware, Live CD's, backups, are in my top 10