You can always reinstall grub from a live USB.
Also, can you elaborate what you mean by preinstalled linux? Do you mean you have a machine with some OEM linux distro? If so, which distro is it?
Edit: You can format using gparted on a live USB. If you are familiar with the command-line, you can use a command such as fdisk (or gdisk for GPT partitions) to delete the partition and create a new partition in it's place, then use the mkfs.ext4 command to create your file system.