Converter does not support Vista, since you have the Enterprise version you could try a cold-clone and see if that works.
Also you could try ultimate P2V...
http://www.rtfm-ed.co.uk/?page_id=174
What platforms can Converter be installed on?
VMware Converter 3 can be installed on the following platforms: Windows XP Professional, Windows 2003 Server, Windows 2000 Professional, Windows 2000 Server and Windows NT SP6+ (IE5 or higher required)
What import formats does Converter support?
Source formats supported include: Physical Machines running supported OS, Microsoft Virtual PC (version 7 and higher), Microsoft Virtual Server (any version), Symantec Backup Exec System Recovery images (also Ghost 9 or higher), VMware Workstation 4.x virtual machine (compatible with VMware GSX Server 3.x), VMware Workstation 5.x virtual machine (compatible with VMware Player and VMware Server 1.x), VMware ESX Server 3.x, VMware ESX Server 3.x (when managed by VirtualCenter 2.x), VMware ESX Server 2.5.x (when managed by VirtualCenter 2.x)
What export formats does Converter support?
Destination formats supported include: VMware Workstation 4.x virtual machine (compatible with VMware GSX Server 3.x, ESX Server 2.5.x), VMware Workstation 5.x virtual machine (compatible with VMware Player and VMware Server 1.x), VMware ESX Server 2.5.x (when managed by VirtualCenter 2.x), VMware ESX Server 3.x (when managed by VirtualCenter 2.x), VMware ESX Server 3.x Note: VMware ESX Server 2.5.x when managed by VirtualCenter 1.x and VMware ESX Server 2.5.x unmanaged are not supported
What are the supported guest operating systems?
The following 32-bit guest operating systems are fully supported by VMware Converter 3: Windows NT, Windows 2000 Professional, Windows 2000 Server, Windows XP Professional, Windows 2003 Server.
The following 64-bit guest operating systems are fully supported by VMware Converter 3: Windows XP Professional, Windows 2003 Server
Support for the following guest operating systems is Experimental. VMware Converter 3 can clone source images containing these operating systems, but the destination virtual machine may or may not work without additional configuration after import. In particular, if the source image contains unsupported hardware, you may need to modify the configuration of the destination virtual machine before using it: Linux, Windows NT 3.x, Windows ME, Windows 98, Windows 95, MS-DOS
