Having ongoing problems with an Acer Quad Core system at work (3 yr old machine). System did not want to boot. It was locked on BIOS. Went through normal procedures and felt crummy 250W power supply was probably DOA. Replaced the power supply with a 400W. Initially I booted windows 7 and everything seemed fine. The next day on boot it makes a long beep/screech sound and as it starts to boot, it turns right off. Any ideas what might be the issue. The graphics card should be fine but we also have onboard graphics to check. Didnt matter same issue. I appreciate any ideas.