If you delete the delta (snapshot) files, you will loose all the modified data!
The reason for the data growth is the way "Delete All" worked before ESX(i) 4.0 U2.
If the crash did not destroy your VM, the easiest way to get rid of the snapshots is to update the host to U2, create another snapshot of your VM and then use "Delete All". Assuming you don't use thin provisioned disks, this should work with no additional disk space needed.
André