this post was submitted on 30 May 2026
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If the PC has been offline and unplugged for years, the CMOS battery on the motherboard is probably dead. This battery maintains the time & date information, as well as the BIOS/UEFI configuration settings (which includes the boot device order).
Replace the battery (usually CR2025 or CR2032) and then review all of your BIOS settings, especially the boot devices, and also verify that the available RAM is what you expect.
Also, this is a Windows XP machine? You should check the motherboard and power supply for signs of the capacitor plague:
Also, a final educational video