Delete partition

i partitioned my disk, i intended using one with the OS (window xp) and the other partion for storage (backup).
i mistakenly installed the os on the storage partition i then delete the partition from the disk management window.
Now each time i bootup i do have a menu option to choose which OS to use. I guess it is also refering to the deleted OS on my storage partition which has been deleted.

I don't want to be doing this again pls how do i get rid of this os which i have deleted