Hi Jens,
in situations where are no snapshots present in snapshot manager the proper steps to cleanup all obsolete snapshots entries in machine directory follow this KB:
VMware KB: Committing snapshots when there are no snapshot entries in the Snapshot Manager
Just short list ...before you will start new conversion process I would recommend:
1. Rigorously clean you physical machine from any 3rd party monitoring software which is bound to physical hardware of your machine (RAID config utils etc...)
2. Remove/uninstall any unnecessary 3rd party software from machine (including antivirus SW etc...)
3. During/before conversion try to minimaze load and changes made to the OS ...
For complete checklist see:
VMware KB: Troubleshooting checklist for VMware Converter
Regards,
P.
