Hi Roland,
I got it working! The trick is in the name of the disk itself. Here's how I got it working. I think step 4, 5 and 6 is more relevant. Thanks.
1. Install vmware-workstation on my desktop (version 9)
2. add netapp 8.1.1 ESX version (vsim-DOT811-7m-esx) as VM to my vmware-workstation
3. right click manage and change hardware compatibility to workstation 9,,,
4. right click settings -> select harddisk 4 -> click utitlies -> compact
5. export as OVF template
6. import this OVF template to ESX5.1 (from web client) giving it a new name ie. test1
7. power on!
Regards,
Chakrit