I don't know of any scripts but it wouldn't take that long to figure out which disks go with which VM's and then figure out if the VM's are registered or not. I think it would be worth it to verify for sure so no important data is accidentally removed.
The summary tab of each VM will show all the datastores that VM is using. Browsing the datastores you can look at the time stamps of files such as the vmware.log file to see if it has been used recently or not.
the command I use to see all the vmdk files referenced by all the vmx files on a particular system is
cd /vmfs/volumes
grep -r vmdk //*.vmx | more
Hope that helps.
Hanna
Hope that helps,
Hanna
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BSCS, VCP2, VCP VI3, VCP vSphere, VCP 5
https://www.ibm.com/developerworks/mydeveloperworks/blogs/vmware-support-ibm