Computer statup troubleshooting

P: My computer has no power and won't start.
A: As serious as this problem may seem, a computer that won't start isn't all that serious. Check the power cord and see if it's loose at both ends. Check if your computer power supply has a switch and make sure that is switched "on". Also make sure the surge protectors, outlets and fuses are ok. Try pluging your computer directly into the wall outlet.
Your next step is to open the computer case and check the motherboard. Most motherboards have a led inside that will stay on even if the computer is turned off. If this led is on that means your computer receives power and the problem is elsewere. If not, check the power supply with a power supply tester, you may have a dead PSU. Also verify your motherboard for unplugged cables, make sure that the motherboard power cord is attached to it's socket.

P: I have error messages before starting windows.
A: Most of the error messages indicate a minor problem. If an error message offers Last Known Good Configuration or Safe Mode, the error is about windows' startup. Selecting Last Known Good Configuration will solve your problem. This is mostly caused by a hardware change in your system (a hardware item recently connected).
If you got an error message regarding your keyboard check it's cable and make sure that all the pins of the connectors are straight. If the issue persists buy a new one. I recommend Razer in the gaming area and Microsoft for other users.
Memory and parity errors indicate problems with your Ram memory modules. Remove them and try changing their slot or check the slot for dirt. Clean it with a soft brush and vacuum, but be carrefull and don't touch anything with the vacuum cleaner.
If the computers starts you have solved the problem, if not, you Ram module can be damaged.
Unexpected Interrupt in Protected Mode. This message appears when you've made an incompatible change to your BIOS(Basic Input/Output System). You solve it by entering BIOS and look for a way to reset BIOS settings to default.
NTLDR missing. NTLDR (NT LoaDeR) is the first file loaded in the boot process. Restore the file from Windows XP CD-Recovery Console. At the command prompt type "cd.." and press enter. Write the letter of your CD drive and press enter. Type "cd 1386" and press enter. Type "copy ntldr c:" and press enter. Type "copy ntdetect.com c:" and press enter. After copying type "exit" and press enter. After restart, your pc should be ok.

P: I get a beeping sound from my computer
A: When something goes wrong that causes BIOS to be unable to start, it uses specific sounds to give you a clue of what is going on.
New hardware.Check your hardware to see if everything is in place. Reboot your computer. If the beep continues, remove the new hardware and see if the beep goes away.
Beep codes.Ussually your motherboard documentation contains information about your BIOS version. Knowing that, you can check on the internet for the problem behind the beeps.

P: Error messages after windows starts
A: Check windows utilities. Press F8 before windows boots (check your documentation if this key doesn't work) to launch Windows Advanced Options Menu. Select Enable Boot Logging. When windows starts, go to c:/windows, open ntbtlog.txt and browse for error messages. Work in safe mode to repair errors.
Safe Mode. Select it from windows advanced options menu. Safe mode loads windows with a minumum set of drives and processes to be more effective. Check your pc for malicious software using an antivirus scan and check your hard drive for errors and bad sectors. Reboot your computer. If that didn't solved your issue go back to safe mode and unninstall any program you recently added to your pc. Also try to restore your computer to an earlier date. To do that go to Start-All prgrams-Accessories-System tools-System restore.
Last Known Good Configuration. If you can't do a system restore, try to select Last known good configuration from the Advanced options menu. Your registry and device drivers will roll back to the last setting under which your computer had no issue.
Windows CD. Use it to repair your operating system. Press any key to boot from it (if options doesn't appear go to BIOS and set your CD drive as primary boot device). When prompted press enter to enter windows setup. Press F8 to accept license agreements and then press R to repair the selected windows installation when prompted.
Recovery console. Boot fromk your windows cd. Press R from the welcome screen. Enter your administrator password if required. At the command line, delete your existing registry files by typing "delete c:\windows\system32\config\system". Repeat for times, but instead of "system" enter: "software", "sam", "security" and then "default". Now copy the old versions of those files by entering "copy c:\windows\repair\system c:\windows\system32\config\system". Repeat four times with same words as I mentioned earlier. Type exit, press enter and reboot.

P: My computer is restarting
A: Hardware. Your computer may fail to boot if your memory modules are not well placed in their slots. Check the clips at both ends of the memory module. If the clips are not closed, press that end of your memory module and close it. Restart your pc.
Check all the power plugs from your power supply to your motherboard and other components to be connected properly. Listen for your hard drive to start spinning. If you don't hear anything, it may be faulty or disconnected from the motherboard. Also, be sure the fans on your motherboard or graphics card start spinning. If any component don't seem to responde try replacing it.
BIOS. If settings in BIOS have changed or become unstable, you have to reset the settings. Restart and go to BIOS. Look for options like "Load Defaults", "Load optimized defaults", "Load fail-safe defaults". First try loading Optimized Defaults, and if your computer fails to start again, load Fail-safe Defaults. If you don't have a choice just load the default settings.
Sometimes your computer won't leave you to access BIOS. In this situation, you have to reset BIOS manually.
The CMOS (complementary metal-oxide semiconductor) memory retains your computer BIOS settings and ca be reset by moving a jumper on a three-pin header on the motherboard and, after a short wait, moving it back to it's original position.
Restarting without error messages. If your system is infected with a virus or malware you may never see an error message that can provide clues. Windows is set to restart any time it encounters a critical error. By disabling this can show your the error messages. To change that, boot your computer into Safe mode and access Control panel, click System icon, Advanced tab and the Settings button from the Startup and Recovery section. Next deselect Automatically Restart checkbox in the System Failure portion. Click ok and again ok. Restart your computer. Now when your computer encounters an error, it will remain on screen.