ESX 3.5. Use clone to backup. Go into the vm directory which suppose to be in the corrected data store directory. Grep scsi on *vmx file to identify which disk u want to extend. First one should be C: and second should be D: etc etc.
# vmkfstools -X 60G virtualdiskiwanttoextend.vmdk
Refer here. Careful with the number you choose. Above example means change the disk capacity to 60GB, not by 60GB.