Just to clarify, if you want to exclude entire VMs and you use the labels approach that uidzer0 suggested, it is simply a matter of changing the search query for the Alert Scope like below
vm.vol.freeSpacePercentage:[0 TO 5] vm.powerstate:poweredOn vm.IsExcluded:"No"
If you want to exclude a filesystem with a certain name (let's say X:\) , again you can again simply change the search query for the Alert Scope like below
vm.powerstate:poweredOn vm.vol.freeSpacePercentage:[0 TO 5] -vm.vol.mountPoint:"X:\\"
However, if you want to exclude a specific volume on a specific VM, I don't believe there is another way of doing it that.
