Complete Guest Sound Loss

[Zadok]

So I've booted up and begun playing with my virtual machine, which worked beautifully for about 30 minutes. But in the middle of adjusting screen resolution settings for an old game that I had installed and successfully run once, I lost all sound from my guest and haven't been able to restore it despite probing through the audio settings. Any ideas where to start?

VirtualBox 5.2.8, Guest Additions installed
Host: Win10 64 bit, 12G memory
Guest: WinXP 32 bit, 512MB memory