It is not easy to diagnose that kind of problem, but I can give you some pointers to narrow down the problem. *
1. First, remove the hard drive, wireless card, and CD drive to see if you can get it to post
2. Getting any kind of beep sequence is a good thing. It says that the CPU is still working and the problem is another peice of hardware. You were right to check the RAM, but sometimes a slot can go bad so make sure you try each memory stick in both slots.
If neither of these help, it is likely that that it is the motherboard. The motherboards on the dv2000-dv9000 series laptops have a lot of problems. I have been able to fix them, but not permanantly as the heat reflow trick but, it will only give you a month or two before it will do the same thing again. It is better just to replace the motherboard or another the system if you just want to smash it with a hammer.
I can post a photographic guide to this repair but in the meantime you can try following these instructions if you'd like.
1. Disassemble the laptop and remove the motherboard from the casing.
2. Use a heat gun on high for 15 seconds on the intel chipset and nVidia video chip.
3. Wait 10-15 minutes for both to cool down.
4. Turn over the motherboard and use the heat gun for 15 seconds to overheat the same areas you just did on the topside.
5. Wait 10-15 minutes for both to cool down.
6. Reassemble laptop and turn on.