On starting my Acer PC , it is switched off aftre one beep. No BIOS display

One beep Normal POST, computer is ok.
Test your PSU power supply unit or replace it if your power supply units fan is not working your PSU is faulty http://pcsupport.about.com/od/toolsofthetrade/f/powersupplytest.htm One bad lead can cause a computer to continue on a cycle of restarting or to shutdown or fail to detect/ boot up a computer hard drive WARNING: Before you start troubleshooting remember that you are dealing with electricity that can KILL. http://www.kitchentablecomputers.com/static.php - rules Only work inside the computer case when the power has been switched off and disconnected. Never open the power source. Some of the below steps recommend removing physical parts within the computer. While in the computer it is highly recommend that you be aware of ESD and its potential hazards Test all leads that attach to your hard drive power and data cables IDE SATA the leads from your MOTHERBOARD TO YOUR HARD DRIVE make sure they have a secure dust free connections and are not faulty or just replace them they could be faulty Make sure all leads that are attached to your dvd\cd floppy drives have secure connections and are not faulty or just replace them they could be faulty. Computers need power and data to travel through every working device to continue its cycle and have an end so any faulty leads will end up with a computer error. Even something as small as a faulty electrical or fan lead can cause you problems Motherboard and a Hard Drive any leads between them will fail before your motherboard or your hard drive if its a flat ribbon 40 pin type IDE replace it this will be the first to fail. Check all electrical power input and extensions make sure they are securely seated even the cd/dvd floppy drives need to have current go through make sure these drives are working also check the Cmos battery and computer RAM modules make sure they are securely seated with no dust built up or in the sockets on some motherboards cmos batteries are soldered in. Check you CPU central processing unit make sure its securely seated and has thermal paste it might be getting to hot the thermal paste will help disperse the heat Thermal compound is a sticky paste that is placed directly onto the CPU. http://www.hardwaresecrets.com/article/Thermal-Compound-Roundup-February-2012/1490 Allowing for a more direct heat transfer between the CPU and HEAT SINK and preventing air gaps from forming between the CPU and heat sink. Another possible reason could be a memory dump you might be running to many programs at the one time putting to much strain on the CPU central processing unit. If you can get your computer stable enough scroll to bottom toolbar bottom of screen right click select task manager applications you will see whats running if you see anything you dont need running select end now also under processes see what is ticking over again if you see something you don't need to be running end now or you might uninstall that program and some unnecessary programs not having enough computer ram can cause memory dumps If you are not sure if a module is right for your system use the Crucial Memory Advisor tool for a list of guaranteed compatible modules. first you will need to select the manufacturer from a drop down list then select your product line from a drop down list then select the model then click find it will take you directly to compatible ram also you will have an option to scan your system you should always for a guarantee on any ram modules when purchasing them or buy working pairs if possible. You might have a virus or malware. Download at least one of these of course it will depend on your operating system. http://www.majorgeeks.com/Microsoft_Security_Essentials_for_Windows_d6242.html microsoft security essentials your operating system must be registered Win7/Vista/XP 64 bit http://majorgeeks.com/downloadget.php?id=4281&file=1&evp=dbb3b0aebe6a6a4ff18089a6489a5e62 anti malware free edition Win XP/2003/Vista/Windows7 http://windows.microsoft.com/en-US/windows/products/security-essentials/product-information malware protection http://100-downloads.com/download.php?p=615 windows xp microsoft security essentials http://100-downloads.com/download.php?p=614 windows 7 microsoft security essentials Capacitors look like small metallic canisters and they are found in many different computer components including computer monitors, computer motherboards, video cards, power supplies and a variety of other consumer products. A bad capacitor can cause a variety of computer problems, but if you can identify the faulty capacitor you may be able to replace it and save your computer.

Capacitor
Capacitors, sometimes also called condensers, are used to store energy in an electric field. In the context of computing, capacitors are used to block the direct current being circulated around the motherboard. A typical capacitor should last up to 15 years, but some computer manufacturers use substandard capacitors resulting in shorter lifetimes. Computer Problems b> When a capacitor has gone bad on a computer you may experience a large range of problems. The computer may have trouble booting up, or it may shut down without notice after running for only a short period of time. The most common problems associated with faulty capacitors are that they cause unexpected computer crashes and general reliability issues ranging from read/write issues to distorted screen images. b> Identifying a Bad Capacitor b> To identify a bad capacitor you will need to open your computer case and locate the capacitors on your motherboard. A bad capacitor may exhibit swelling at the top or the base of the capacitor or it may sit at an awkward angle with the motherboard, so compare the various capacitors in your computer in terms of and placement. Additionally, a bad capacitor may have a funny smell or it may have a brownish residue leaking from the top or the base. b> Prevention b> Manufacturers claim that capacitors may go bad because a computer is not receiving enough power from a power supply, because of an overclocked processor or because a computer is operating in an environment with too much heat or humidity. However, some capacitors prematurely fail due to faulty work on the part of the manufacturer. If you have a bad capacitor be sure to do research as to the lifespan of other products made by your manufacturer. Identifying bad capacitors http://www.youtube.com/watch?v=ngA4k32jLGc Capacitor replacement http://www.youtube.com/watch?v=s0Pn2tEjY04 How to check a capacitor http://www.youtube.com/watch?v=U4tnHA0phcc Replacing a leaking capacitor http://www.youtube.com/watch?v=s0Pn2tEjY04 Could be a problem with the Hard Drive or the Hard drives PCB http://www.onepcbsolution.com/ Hope this helps.

How old is the computer? Have you changed the CMOS battery? Reseat Memory Mods,possible bad Memory mod. May be a bad PSU. Try Acer support , Troubleshooting procedures. If it on in years the PSU is a likely place to start. Do you have a Multimeter to verify voltages. If , when you push the on/off button the fans spin, the LED's blink, and then a shut down, all power off. Power supply, system board, keyboard. Take a look at the Beep Codes: http://www.bioscentral.com/beepcodes/phoenixbeep.htm# That should keep you busy for a while.