Well no you don't need to delete everything "manually" if you mean go through directory by directory and file by file. Once you have a functional SSD with an OS on it take your original C drive (which you do not connect till AFTER boot so as not to get the PC confused, your new SSD is going to be the C: drive with the OS).
Win X > Disk Management > right click on the old drive select "format", then NTFS, Default, "perform a quick format" all of which will likely be preselected. If it asks make a boot drive (I think it will see the disk used to be a boot drive) say no.
That will clean things up and incidentally make it so your old drive is no longer seen as a boot drive. For the purposes of ordinary people all the data will be eliminated. The FBI could pull some data off such a drive, but for us, it's done. Then you can use it to store your files.