I want to know is that possible to reduce the size of the virtual disk like at that time when the vm is created the size of the disk was 40gb and now as soon as it is created or after copying some data in that disk i want to reduce the size of this vDisk is that possible or not??????
The best solutions to do it is with converter standalone see http://vsphere-land.com/tips-tricks/re-sizing-virtual-disks Method 2.
follow link download of converter http://www.vmware.com/go/download-converter
You can reduce size of the virtual disk, link blow is procedure to help you reclaim unused space in the virtual disk (with some limited requirement)
You can use VMware Converter to shrink the virtual disk and do the conversion
Please have a look followings link..