Unfortunately the version/build you are using is too old to safely run "Delete All". However, after taking a second look at the files, it looks like there was an issue on Feb, 25th with the snapshot creation (a lot of dump/gz files). Maybe the first snapshot isn't even in use!?
To find out about this, you need to connect to the host using e.g. WinSCP and download some files. These are *.vmx, *.log, *.vmsd, *.vmdk (only the small ones - a few hundred bytes - without flat or delta in their names). Once downloaded, compress/zip these files and attach the .zip file to a reply post. In order to attach files, you have to click the "Use advanced editor" link.
How does the other VM on the datastore look like? Does it also have snapshots. Please post a screen shot of the datastore browser window for this VM too. Maybe there's another option to get rid of the snapshots, e.g. by temporarily powering off the VMs to free up disk space or by migrating the second VM to another datastore (if there is one)!?
André