We need more information.
What brand of computer are you using?
What operating system are you using?
If you have all your installation disks you could format your drive and start over again.If you are using win 9x you can use boot disk and use: A: format C:\ mbr this will rewrite the Master Boot Record.
If you have a HP or Compaq you need the program from the HP web site,those brands have a special boot.
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