I've had HP pavilions the last 4 or 5 PCs I bought. I disable all those HP services. However I don't recommend changing a bunch of things at once on a PC unless you have a way to put them back, such as an image backup.
You might go on a site like Black Viper or another to see descriptions of services. I would advise making a text log of every change, or at least making a restore point and/or image backup so you can undo things if you make a problem. If worse comes to worse you want to be able to boot a CD and restore your system partition from a backup image.
HP diagnostic services aren't that risky, but anytime you mess around disabling services you can hose things so your system may not boot(if you should accidentally disable the wrong thing.)
Essentially, these HP thingies are checking a system that isn't broken. It's a waste of time. If stuff goes wrong you'll know it without the diagnostic.