After you've accidently deleted your grub/ formatted the linux partition or deleted your win boot loader. Your system will not boot and give you errors like Grub Rescue or Grub Error etc.
As a result you will not be able to log into windows or any linux Destro.
If you happen to have a live CD of Win / the respective linux destro installed then you'll need to follow other methods.
Suppose if you dont have any live cd and not able to boot
You'll need Super Grub
Step 1: Go to this website http://www.supergrubdisk.org/super-grub2-disk/
Step 2: It's 1.4 MB Download it and burn it on a CD or put it on the USB by this METHOD
Step 3: Boot the CD/USB the menu will appear, select "Detect any Operating SYSTEM"
Step 4: It may display Unknown FS (Filesystem) Just give it some time . It'll show you a list of OS that's on your System. Select which ever you want to boot inn. Suppose you wan WIN 7/ Win vista/ Xp select the appropriate option and hit enter.
Step 5: Your system will boot into the windows installed on your system.
Note: You can use this CD to boot each time. It's only temporary. i.e After your restart the system without the CD it'll show you the same grub rescue / error . To prevent this there are grub rescue methods for LINUX based on the diff linux destro. Google it.
For windows.
step 1: Download Easy BCD http://neosmart.net/EasyBCD/
step 2: Select Bootloader setup
step 3: select Fix MBR
your done!.
Note: this will write only the windows partition to the loader all your linux partition entries will be lost.
