System restart automatically in booting process
1)Boot from cd
2)Select First Repair
3)Type map to know which drive was CD ROM drive
4)suppose cd rom drive is e then type e: press enter
5)type chkdsk /r c: and press enter
after 100% compleated type exit and automatically restart the m/c
in case of NTLDR Missing error
same steps up to 3 rd step
4) type copy ntldr c: and press enter
5)type copy ntdectet.com c: press enter
