You can download the tool from http://kb.vmware.com/kb/1023856 (see "Attachments").
To convert the virtual disk to an ESXi supported format run
vmware-vdiskmanager.exe -r "Digipos Book PC SP1.vmdk" -t 4 "Digipos Book PC SP1-new.vmdk"
then upload the two newly created files ("Digipos Book PC SP1-new.vmdk" and Digipos Book PC SP1-new-flat.vmdk") to the ESXi host and edit the VM's settings, i.e. remove the wrong virtual disk and add the correct one.
Please be aware that the resulting virtual disk will have a size of 40GB.
André