If you don't care to do a full blown nuke of the drive you can always do a standard clean and format.
Run command prompt as administrator.
Enter the following pressing the enter/return key after every entry.
diskpart
listdisk
select disk # (# being the SSD)
clean
create partition primary
select partition 1
active
format quick fs=ntfs
exit
exit
This will clean and erase the drive and all partitions along with formatting it.
However, if you are for some reason trying to erase this disk while you are using it (i.e. it is the drive that has the OS on it and you are booted into that OS) then that would be the cause of your problem.
Alternatively, you can go the "I won't let the government get their hands on my data" route and...