You want to shrink an too big harddrive on your VM?
Ok, lets go:
1.) Create an Harddrive in your VM which does have the desired size as second Drive
2.) Boot the VM with an Parted Magic ISO (http://partedmagic.com)
3.) Choose GParted and size your existing Harddrive down so that it will fit into the new Drive
4.) Choose Clonezilla, start for Local Disk, Local Disk to Local Disk, choose your old Disk as Source and the new as Destitination and Expert Modus.
4b.) Don't change anything in Expert, just klick through and accept the new MBR and Co.
5.) After thats done, you're done! Shut down, remove the first Harddrive (just remove from VM, NOT ERASE FROM ESXi!) and select the "new" Drive and set it to the SCSI Path the old one was (0:0:0) or so - fire it up! It should boot.
If it doesn't, get the new drive again to second with the second scsi path, insert the old drive as first again, and try again. Mostly works on second trial.
PS: If you got an Windows VM, try to use Acronis True Image Home 11 and its harddrive clone function. Works better on MS Products.