I realize this is an older thread, but just in case anyone just getting started with virtualization is looking for help, here is my experience.
I would go with VMware Converter Standalone as the simplest solution because it works. If you can't do a hot migration, then try a cold migration. If that still doesn't work, or if you need another workaround due to security zoning on your network, then I've used Acronis True Image as a last resort.
And yeah, the typical answer in this VMware-centric forum is going to be the VMware solution, but sometimes you may have to get a little creative if it just won't work. Everything is usually based on requirements. ATE wasn't a one step process though, and I had to have a "transient" location to export images to before importing to vCenter (and it will connect to vCenter or a host). Sometimes being able to do this because of security/network zoning and firewalls in between, may be the better way to go, otherwise you're looking at swiss-cheesing the firewall for converter ports if you don't already have rules in there for it. Out of 400ish P2Vs, I maybe only had to use this last resort 10-15 times (old HP BL20 blades ... grrrrr).
If the server is really small or provides a simple re-creatable service (like an IIS server or "Jump Box", and is way overdue for an OS upgrade), you also have the option of building a new VM to take the role, and migrating off the hardware altogether. Much cleaner process than having to rip out all the HW specific software like [insert vendor name here] tools/agents, and having to clean out hidden devices in your device manager.
No, i'm not asking for hardware requirements... give me workload requirements.
