model name : Intel(R) Pentium(R) Dual CPU E2200 @ 2.20GHz clflush size : 64 cache_alignment : 64 address sizes : 36 bits physical, 48 bits virtual
That CPU is clearly 64-bit: https://ark.intel.com/products/33925/Intel-Pentium-Processor-E2200-1M-Cache-...
I don't know what could have gone wrong to make an installer think it wasn't 64-bit capable. I don't think there is such a thing as a socket LGA775 motherboard that doesn't support 64-bit CPUs. It may even be that there is no such thing as a 32-bit CPU to fit a socket LGA775.
Could it be that the HD had a 32-bit OS installed and was trying to install in upgrade mode? That might explain why the / filesystem was EXT2, and why you wound up with / filesystems routinely losing space.
Maybe that model motherboard was released with a BIOS too old to properly support the E2200 CPU, and needs a BIOS update. You can find the installed BIOS version via BIOS setup, or from the POST screen, or use dmidecode.
Testing for 64-bit support shouldn't be hard or need "techie" help. Fetch and burn a 64-bit network install .iso instead of a DVD, a small fraction of download size and time, and see what happens in clean / install mode.
Verifying 64-bit support would be another use for the Knoppix DVD or CD I previously mentioned that a Gparted CD wouldn't likely be designed to do.