Kernel.org: 5.2.1
sid (unstable): 4.19.37-6
buster (testing): 4.19.37-5+deb10u1
stretch (stable): 4.9.168-1+deb9u4
jessie (oldstable): 3.16.68-2

Debian GNU/Linux device driver check & report

HP: Compaq dc7800p Small Form Factor

PCI IDWorks?VendorDeviceDriverKernel
808629b0YesIntel Corporation82Q35 Express DRAM Controllerintel-agp
808629b2YesIntel Corporation82Q35 Express Integrated Graphics Controlleri915v2.6.32-
808629b3Intel Corporation82Q35 Express Integrated Graphics Controller
808629b4Intel Corporation82Q35 Express MEI Controller
808629b6Intel Corporation82Q35 Express PT IDER Controller
808629b7Intel Corporation82Q35 Express Serial KT Controller
808610bdYesIntel Corporation82566DM-2 Gigabit Network Connectione1000ev2.6.25-
80862937Intel Corporation82801I (ICH9 Family) USB UHCI Controller #4
80862938Intel Corporation82801I (ICH9 Family) USB UHCI Controller #5
80862939Intel Corporation82801I (ICH9 Family) USB UHCI Controller #6
8086293cIntel Corporation82801I (ICH9 Family) USB2 EHCI Controller #2
8086293eYesIntel Corporation82801I (ICH9 Family) HD Audio Controllersnd-hda-intel
80862940Intel Corporation82801I (ICH9 Family) PCI Express Port 1
80862942Intel Corporation82801I (ICH9 Family) PCI Express Port 2
80862934Intel Corporation82801I (ICH9 Family) USB UHCI Controller #1
80862935Intel Corporation82801I (ICH9 Family) USB UHCI Controller #2
8086293aIntel Corporation82801I (ICH9 Family) USB2 EHCI Controller #1
8086244eYesIntel Corporation82801 PCI Bridgei810_rng
80862914YesIntel Corporation82801IO (ICH9DO) LPC Interface ControlleriTCO_wdtv2.6.26-
80862920YesIntel Corporation82801IR/IO/IH (ICH9R/DO/DH) 4 port SATA IDE Controllerata_piixv2.6.25-
80862926YesIntel Corporation82801I (ICH9 Family) 2 port SATA IDE Controllerata_piixv2.6.25-

Initially  sound did not worked in Lenny with internal speaker (alsa).
After creating the file /etc/modprobe.d/modprobe.conf with one line
options snd-hda-intel enable=1 enable_msi=1 single_cmd=1 power_save_controller=1
got the internal speaker working.
Sound-System
=============
# lshw -C multimedia
  *-multimedia
       description: Audio device
       product: 82801I (ICH9 Family) HD Audio Controller
       vendor: Intel Corporation
       physical id: 1b
       bus info: pci@0000:00:1b.0
       version: 02
       width: 64 bits
       clock: 33MHz
       capabilities: pm msi pciexpress bus_master cap_list
       configuration: driver=HDA Intel latency=0 module=snd_hda_intel
# aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: Intel [HDA Intel], device 0: AD198x Analog [AD198x Analog]
  Subdevices: 0/1
  Subdevice #0: subdevice #0
card 0: Intel [HDA Intel], device 1: AD198x Digital [AD198x Digital]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

# grep -i codec < /proc/asound/card0/codec#0
Codec: Analog Devices AD1884
 (2009-06-07 17:30:16)