you can't delete a disk that is attached to an instance.

[556]

My VM instance has already been deleted.
When I want to delete its disk, the button keeps playing "you can't delete a disk that is attached to an instance."

Any one face this similar problem before?
how to solve it?

[DamianS]

Hi,
Q1: Did you've check which VM holds mentioned disk? 
Q2: Are we talking about boot disks or additional disks?

I'm asking because I've tried to replicate your problem and I've got this alert when
1. VM was powered off instead of delete and boot disk wasn't deattached from powered off machine.
2. My additional disk which was created separately was also attached to second machine. 

cheers,
DamianS

[556]

Hi DamianS,

A1: Yes, I checked. But the VM is indeed already deleted.
A2: boot disks.
(this is exactly the strange point. The VM is deleted but its boot disks still exists and cannot de deleted.)

Above all, to solved the problem, finally I had to delete the entire project. Deleting the whole project may be a clumsy solution but al least it solved my problem and the disks don't cost my money anymore.

Hope this help.