I used to have Windows Vista & Ubuntu 12.04 on dual boot. Accidentally, I deleted the Linux partition and landed on Grub rescue on the next boot. The tricky thing for me here is I have been trying to boot through LIVE CD/USB of the ubunutu version, other linux versions but in vain. What happens is, it appears as if it reads the CD/DVD drive or the USB flashes for a while when trying to boot through LIVE versions but the Grub rescue appears after a while. The only option I could think here is to remove the hard disk and connect to the other laptop I have through USB and reinstall a fresh OS. Please suggest me a way to boot through the DVD/USB again. My laptop is Sony VAIO CR32 series.Thanks.
Boot order is determined by BIOS and what medium to boot from is decided by the BIOS before GRUB is invoked. I.e. BIOS tries the devices one by one in the order specified in the "boot order" setting, once it finds something resembling a valid boot record it passes the control to the bootloader on that drive.
So if you see GRUB prompt at all it means that either your boot order is incorrect, with the HDD being on the top, or that your boot medium does not contain a valid boot record.
Can you test your CD/USB to see if you can boot another machine from it? Also please double-check that in your BIOS settings the removable medium (CD/flash drive) has priority over the HDD.
Alternatively, yes, you can remove the drive from the machine, plug it into another one and fix the boot record from there.