Unfortunately, many older Dell's that came with XP, do not have Vista or later drivers (e.g. many old Dimension models). I used to work the Dell user forums and those that were not Vista/Win 7 compatible required installing a separate sound card that was compatible. This sounds like what yours may be. If the sound is compatible Windows will install the generic, basic function, High Definition Audio Driver. If that was not installed most likely it is not compatible.
My Computer
Computer type
PC/Desktop
Computer Manufacturer/Model Number
My Own Build
OS
Windows 10 64 bit
CPU
Intel i7 6700K
Motherboard
ASUS ROG Maximus VIII Hero
Memory
16GB Corsair Dominator
Graphics Card(s)
Intel CPU Graphics
Sound Card
RealTek
Monitor(s) Displays
27" Dell S2719dgf
Screen Resolution
2560X1440
Hard Drives
1 TB Samsung 850 EVO SSD for Win 10 Pro
500GB Samsung 850 EVO SSD for Win 10 Insider
2 TB drive for backup
PSU
EVGA Supernova 750G2
Case
BeQuiet Silent Base 600
Cooling
Deepcool Captain 120EX
Keyboard
Microsoft Wireless 2000
Mouse
Microsoft wireless
Internet Speed
100 MB/sec (Cable)
Antivirus
Microsoft Defender and Malwarebytes
Browser
Edge/Firefox
Other Info
Cakewalk (Sonar) by BandLab and Studio One 4.1 Pro recording studio software. MOTU 896Mk3 Hybrid recording interface, Frontier Tranzport wireless control unit, Behringer X-Touch Control Surface.
Five USB connected optical drives for CD Audio production using Nero BurningROM
