ITExperience.NET

On VMWare ESX3, your VM exists of one or more VMDK files (extension .vmdk) and one or more flat vmdk files

It might occur that you may corrupt, lose or accidentally delete your VMDK files. Without your VMDK’s, you cannot load your flat.vmdk-files. This means you can’t load the VM in your VirtualCenter and you can’t start the VM.
To recreate the VMDK files (whether they are corrupted or deleted), follow the steps on the next link to recreate your vmdk’s (.vmdk):

http://www.itexperience.net/2008/03/03/howto-recreate-vmdk-files/