I know how you feel now, but you have to relax because we are fixing this grub rescue error right away. No too much write-up.

Cause.

You were probably having a windows operating system and decided to install Linux alongside.

Then later deleted the Linux partition through windows.

After restart. You got the message below;

Error: No such partition

Entering rescue mode… 

grub rescue>

First of all, Follow the step below to fix the problem

Step 1 – Load into and installation media

Step 2 – Press Shift + F10 to open the CMD (Command Prompt)

Step 3 – Type “bootrec.exe /fixboot” and hit Enter

Lastly,  Step 4 – Type “bootrec.exe /fixmbr” and hit Enter

We are done.

Restart you PC.

UPDATED

If after restart the PC still gives the same error. Use the following method.

Step 1 – Load into your installation media

Step 2 – Type DISKPART

Step 3 – Type “List Disk” (Usually you’ll see a list of multiple disks, from 0 to 2)

Step 4 – Type “Select Disk 0”

Step 5 – Type “List volume”

Step 6 – Type “Select Volume 1” (This depends on the volume you have your partition on)

Step 7 – Type “List Partition”

Step 8 – Type “Select Partition 1” (This depends on the partition you have your OS on)

Step 9 – Type “Active”

See also, Upgrade Server 2008 or 2008 R2 to 2012