You bought a new sound driver?
Assuming you bought a new card, you will need new speakers.
This is one of HP's propietary componentries.
Basically whats happend is that your original speakers arent self powered (you dont have a seperate power cord for you speakers)
The original sound card also has an internal amplifier so that the sound is boosted to the original speakers.
What you need to do:
1 - return the new sound card you got and get those drivers or,
2 - get new (powered) speakers
PS: The next time someone says dont get a HP, Don't