PC can't boot up; If when, window's logo shows it will start all over again and again?

Dear Sir,

You might have deleted few important files that are needed for the start-up of the OS, try to do a Safe Mode start by pressing the F8 button on your PC when turning on your PC, this will load the least required files to the RAM, then try to run the Windows SetUp program in Windows folder to repair, or if you still have the bootable CD/DVD for the OS then you can insert it in your PC, reset it and it will let you chose to repair the OS.

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