Describe the beeps. Long beeps are usually RAM errors, so try reseating the RAM or using some different RAM. A short burst of four or eight beeps usually is a video card error (kinda sounds like "BeeeeBuBuBup").
General troubleshooting tips:
- As a "just because" jumper the BIOS to clear it, and try turning it on again.
- Have everything unhooked or removed that isn't needed, keeping only power supply (without any drives hooked up), CPU, HSF, RAM, video card.
- Work on the motherboard outside the case, on something padded and nonconductive.
- Reseat all the parts, as in take out the CPU/RAM/video and put them back in.
- Start swapping in known good parts.