The partition layout on the installed disk does not work with your hardware. For older PCs such as this I recommend embedded m0n0wall derivates like SmallWall or t1n1wall.We're hope to get the installer more compatible for 16.1, but it is a low priority item as workarounds like the nano image exist.Nano has had troubles with upgrades in the past. There's a new nano image coming out next week to address issues we still had with the initial 15.7 or the older ones. A test snapshot is here, although it is i386 only:https://pkg.opnsense.org/snapshots/OPNsense-15.7.9-LibreSSL-nano-i386.img.bz2More on brand new nano images next week...