I got it open, by jamming a screwdriver in where the button goes in, and then pressing the good button in the "normal" way.
Yeah, I'm near Bundaberg, and although there is a freecycle list, the only stuff ever on it is usually requests for working cars, requests for working, modern computers, requests for modern/valuable computer parts, baby clothes, old VHS tapes, 10 year old inkjet printers, etc, etc.
Either way, its now back in one piece, with a 40GB HDD, a Pioneer slot-load CD-ROM drive, and a WinModem. The Radeon 7000 is now in my Dell P4. This morning I put Windows Server 2008 Datacenter Edition on the Compaq. I had a Celeron 600 chip inside it at the time, and with that and 384MB of RAM, it not only installed, but also boots without complaint. Performance-wise, its a bit sluggish, but really not too bad, all things considered.