Find all past desktop IP addresses

The Windows DHCP Client service can log this, if you have the Operational log enabled. Some say it is enabled by default, but my limited testing shows otherwise.

This won't help you in the past but it can going forward.

You can enable it in Event Viewer -> Applications and Services -> Microsoft -> Windows -> DHCP Client and enable the Operational log.

After enabling the log "Event viewer --> windows system logs -->filter current log" and choose "dhcp-client" under Event Sources.

Interesting question...

At the very least, the DHCP server should log all the addresses it hands out, if logging is enabled.

Im looking to see if its logged on the client side anywhere, but Im not seeing anything.

As far as I know there's no such log. There are entries for the DHCP client in the system logs, but those seem to take errors and failures only (and won't include manually assigned IPs). What you could try is doing a system restore. If you're lucky, the last restore point is just hours before (or possibly days) and still has the old configuration.

I've found one duplicate question without any clear answer either.