I had installed ubuntu 13.04 and wanted to install 12.04LTS . I knew that directly deleting the Ubuntu partition will delete the linux GRUB and also due to the absence of the windows bootloader it will make the system unable to boot any OS. I had heard about the easy BCD software to create a WIndows entry and MBR. But that procedure went wrong and i deleted the partition without knowing the mistake. The laptop wasn’t booting any OS.
the GNU grub is a pacakage that is installed when installing a linux operating system parallel to a windows OS. This package gives you the choice to boot one of the multiple OS on your system.The grub is installed over the default windows bootloader(that helps booting windows) and hence if the linux OS is deleted so is the grub and the system doesn’t knows where to boot from.The only solution is to add the windows bootloader again into the system.
This led me to do lot of research as to how to add the bootloader. I didn’t have my operating system installation disc either. But my research helped me repair my system back to normal state booting on windows.I learnt a lot of Do’s and don’ts while installing multiple OS.
I had a windows 7 Ultimate installation disc. But mine was windows 7 home premium.It is not a problem if u have a different version CD of your OS. Boot your laptop with that CD and click on repair computer.It detects the fault and automatically installs the windows bootloader. You have to restart and the windows is back to normal.
Another way is, if you have a live USB with ubuntu in it,then boot the laptop through the live USB and install ubuntu on your system.this reinstalls the linux GRUB and you will be able to boot windows or ubuntu.
Once this is done boot Windows and create a recovery disc so that you can boot using those discs if the bootloader is deleted.
Remember not to use system recovery present in your laptop as it will reinstall the entire OS and may sometimes delete the data also.It is best advisable to use the method mentioned above and create recovery discs.
If you haven’t already deleted ubuntu and if you want to then use Easy bcd to add windows entry and don’t delete the partition unless the changes you have made using Easy bcd is found working.