Have you considered ESX4/vSphere (purchase) or esxi4 (free) both products in my view are much better than Hyper-v
I love it when people make unqualified statements like that. Better for what? In the case of ESX/vSphere, I'm assuming that you mean better for spending $2500 per CPU to get the functionality that Hyper-V provides for free. Or in the case of ESXi, better for getting the price of Hyper-V with a lower level of functionality.
Don't get me wrong, I sell and support both solutions, but I have yet to see a company that couldn't meet their virtualization requirements for the overwhelming majority of systems with Hyper-V.
Yes, vSphere/ESX has more features, but the majority of that feature gap are required by a small minority of circumstances.
At any rate, the OP clearly has already looked at VMware solutions and ruled it out for this exercise, as indicated by his previous use of VMware Converter.
Back to the point of the post, if you only want to do a "test conversion" to see if this app will work virtualized AND you don't want to go the SCVMM AND the Disk2VHD tool won't work AND you absolutely have to keep the machine up you can try using a disk cloning/imaging tool to make an image of the server, then restore that image to a Hyper-V VM. You will still have to do some cleanup, but it should work without any issues assuming that the tool you select allows you to clone a live machine.
Once you have verified that the server can be virtualized I would still recommend that when you do the final P2V conversion in an offline fashion OR use SCVMM.
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CompTIA A+, Network+, Server+, Security+
MCTS:Windows 7
MCTS:Hyper-V
MCTS:System Center Virtual Machine Manager
MCSE:Security 2003
MCITP:Enterprise Administrator