If you have Windows os installed then first set your BIOS config to boot from the cd. You should have windows setup cd of the particular windows version. If you don't have one then collect the setup cd from your friend or anyone you know who has the cd. Insert the CD in the cd-rom tray and restart your PC. Then press any key when it is prompted to do. You will see windows setup cd to load, after a while you will see the repair windows option click on it and when prompted select the command prompt option. In the command prompt write down
:-bootmgr.exe/fixboot press ENTER
then
:-bootmgr.exe/fixmbr press ENTER
that's it restart the PC and leave it to boot normally. This process should coverup your problem.