Ok, can you provide us with the exact model name or number of the Hp Pavillion and the same for the speakers please, this will help us with research.
Do the speakers have a power light which shows that they are on + have you checked for a separate on/off switch on the back of one of the speakers, it may slide left to right as opposed to being a turn type of knob.
Would the mb own audio be enough to power these
The speakers are intended to amplify the MBs audio.
would I have to turn something off etc ?
No, not unless you had an add on audio card.
Have you checked the computers own audio settings and can you tell us what operating system you are using please.