Why does Windows show only 16GB usable when I have 32GB installed?

Start by checking the Memory tab in Task Manager. Look for the hardware reserved amount, not just the committed limit. Committed memory includes virtual memory backed by the page file, so a limit near 32GB doesn't mean all 32GB of physical RAM is usable.

Also check whether the BIOS or UEFI reports the full 32GB. That helps narrow down whether the discrepancy shows up before Windows loads.

Power down, unplug the PC and reseat both sticks. Make sure they're fully clicked in, and check the motherboard manual for the recommended slots for a two-stick setup.

If the full amount still isn't usable, test one stick at a time in the recommended slot. That can help distinguish a bad stick from a slot or configuration issue.

Once the sticks are seated properly, run a memory test such as MemTest86. It checks RAM for errors and can help identify an unstable or faulty stick. You normally put it on a USB drive and boot from that drive to run the test.

Check the Windows boot settings too. In System Configuration, open the Boot tab, choose Advanced options and see whether Maximum memory is checked. If it is, clear it and restart. Don't set a new limit there.