Here's a fix for anyone who has a dv2000 HP laptop that gives a dvd drive not detected problem. I first had this problem with Vista 32-bit SP1 (this laptop comes natively with Vista 32-bit). That time the problem with the missing drive became severe enough that I had to restore the computer back to factory specs and the missing DVD drive reappeared.
This time I've installed Windows 7 64-bit. Sure enough the missing DVD is back. Tried the upper and lower filter driver registry hacks mentioned elsewhere, but they didn't work for me. Further searching reveals that the problem here is a bad (S)ATA driver for the DVD Drive. Where to find drivers? Turns out, I went to control panel --> device manager and found something called SATA controller. I went to the option to choose another / alternate driver and actually installed the standard dual IDE driver instead.
Woila! The missing DVD Drive is found. So it looks like the nforce driver is bad. Oh, well everything works for now.
Also, fixed a missing "coprocesser" device manager icon by installing Vista 64 Nforce drivers for dv2000/dv2416 from the hp support and drivers site.
Another pesky problem, a problem with blank LCD when powering on (solved that problem temporarily by reflashing the BIOS - seems F.39 works better than F.3C which is a newer bios).