Trying to Delete Nexenta OS, similar to Solaris
 

Yes, I am trying to delete nexenta from my computer, and it seems that the grub commands aren't the same as the normal bash commands. Can anyone help?

Just install over it. There's no need to specifically remove an OS from your computer. If you want to add the disk space it is using to another OS use gparted off a LiveCD to delete the partitions and expand the other OS's partitions into the empty space (this can be dangerous so back-up your data first).