We had a problem with a template..not being able to turn it on...we would get a file locked error.
Not sure how someone accomplished this but they had used the template VMDK file in a deployed virtual machine. How did I find this out? Using the command shown below, which looks through all the virtual machine config files to find if any other machines were using the file. xpsp2basethin.vmdk was the file in use.
[root@esx3srv0301ph xpsp2base]# egrep -i xpsp2basethin.vmdk /vmfs/volumes/*/*/*.vmx
/vmfs/volumes/499f22e3-2239bc87-25f0-001a6459e0f8/vpcuniversity2/vpcuniversity2.vmx:scsi0:0.fileName = "/vmfs/volumes/499f2335-cd135fea-a4dd-001a6459e0f8/xpsp2base/xpsp2basethin.vmdk"
/vmfs/volumes/499f2335-cd135fea-a4dd-001a6459e0f8/xpsp2base/xpsp2base.vmx:scsi0:0.fileName = "xpsp2basethin.vmdk"
/vmfs/volumes/hdsvpc3a/vpcuniversity2/vpcuniversity2.vmx:scsi0:0.fileName = "/vmfs/volumes/499f2335-cd135fea-a4dd-001a6459e0f8/xpsp2base/xpsp2basethin.vmdk"
/vmfs/volumes/hdsvpc6a/xpsp2base/xpsp2base.vmx:scsi0:0.fileName = "xpsp2basethin.vmdk"
Link to a good KB article with much more on this subject: