Will overclocking the cpu with this program void my warranty. I have an amd64 3800 x2.

Overclocking ANY CPU with ANY tool (be it software, BIOS, jumpers, etc...) will void your warranty! Overclocking as a whole is nearly always outside the warranty, and you should always proceed with caution...-Greg

The other side though is that if you overclock in small steps until you find your overclocking sweet spot, it is extremely unlikely you will kill your CPU, either in the process of overclocking or with long term use that way. If another component in your system fails that has nothing to do with your overclocking (eg. HDD fails), just return your CPU to stock speed before getting it looked at under warranty. The ethical issue comes with where to draw that "has nothing to do with your overclocking" line, which can range anywhere from considering the whole system to be tainted to just the CPU. In general, when you overclock the CPU, you overclock your RAM and motherboard chipset as an unavoidable side effect. If you keep PCI/AGP clock speeds the same, then any other peripheral should not be involved in your overclocking.Gary