1.Boot your computer to the Windows 7 DVD (or to a “Repair CD”). At this screen choose to install now. choose REPAIR
2.Click the button for “Use recovery tools”.
3.Then select “Command Prompt”.
4. Command promt
dispart
select disk 0
list volume
find the CD volume Letter if it is G or F or E
exit
5. on command prompt
G: if CD is G:
cd boot
dir -> see if bootsect.exe is exist
bootsect /nt60 SYS /mbr
exit
6. RESTART