Windows 7, Disk is offline because it has a signature collision

When I switched on today my second hard drive I had the following issue displayed

The disk is offline because it has a signature collision with another disk that is online

Running Diskpart as administrator proved that it was the issue

As you can see disk 2 and disk 4 both have the 00024A91 signature hence the collision.

Following the advise here, I changed the signature of the drive decreasing from 1 unit.

Than I brought back the disk online using Disk Management

And everything went back to normal