I recommend to use the Infrastructure Manager Client (assuming you are using ESXi 3.5, if you have 4.0 I think that is shipped with a managing tool vSphere something) to upload your vmdk file to the data store.
First, create a new virtual machine with corresponding settings for the intended OS. Then, on the summary page in Infrastructure Management, right click on the datastore icon, choosing "browse datastore". That opens a file manager view to the place where virtual machine files are stored. Open sub folder of your newly created VM and overwrite the existing vmdk file by clicking the upload button (make sure you name your source vmdk file as it shows in the datastore).
You have chosen "vmware esx" option in the Acronis converting process, right?