1.If you reinstalled Windows with Linux in your HDD,Windows will be directly startup with not Grub load when you restart the computer,and Linux cannot be startup.
2.If you deleted Linux partitions incautiously,when restart the computer Grub will be loading error and the computer doesn’t boot any startup disks.
This article may help you if you have the problems above.
Grub doesn’t work when you reinstall Windows:
First,go into the BIOS and set the CD to be the first boot device.
then,you need a Linux install CD and boot from the CD.
Open a terminal window after startup,and execute the command:
where “x” is a number presented after execute “find /boot/grub/stage1″
restart your computer,and hope this helps you.
Loading Grub error:
First,also go into BIOS and set the CD to be the first boot device.
then you need a Windows install CD and boot from the CD.
Press R to go to the recovery console when it asks you whether you want install windows etc.
startup disks include Windows will be present to you
enter the number at the beginning of Windows,then you will go to command line.
For XP or NT users:
C:\WINDOWS\cd.. C:\fixboot c: C:\fixmbr
and for DOS based system use “fdisk /mbr”
select the new entry by execute command: