Sorry to hear it's starting to fail beyond battery issues. You still could try going back, sometimes Windows issues may appear as hardware issues (like the diagnostic tool not seeing speakers and mic in the windows device list, marking it down as hardware issue), as software might not get far enough through the HAL (no, not 2001's HAL, but the Hardware Abstraction Layer) to detect actual hardware issues. You might even want to try and turn off the audio chip in BIOS/UEFI, boot windows, and then turn it on again in the BIOS/UEFI. Sometimes that can help too (it's like remove it and plug it in again).
I've only replaced one PC - well mainboard, but often that's considered the core - due to failing from age. One laptop had its GPU die from thermal issues, another laptop i replaced with the end of Windows XP and the lack of power for 7, and then I destroyed a mainboard by being stupid and re-settling the heat sink in a not good way.