MS Hyper-V Server 2012 and converting physical 03 servers questions

Hello,

So I have a question regarding the requirements to convert 4 Physical MS 2003 servers to VM and package them up to run in Windows Hyper V Server 2012.  Essentially, this is what the current IT makeup is of the small firm:  4 servers; DC, File, Exchange 2003, Application.  They are all 5-6 year old Dell servers near end of life and running MS Server 2003.  Unfortunately, this firm has a very limited budget and am thinking of doing the following and need to make sure it’s feasible:

I would like to setup Windows Hyper V Server 2012 on a brand new bare metal server (free version).  Then convert the 4 physical servers to VHD via the disk to VHD tool and package / put them in the new Hyper V 2012 bare metal server disks.  My main concern is, do I need any extra licensing to get these 4 converted servers to run ok?  Or can I just convert them to VHD as is, dump them in Hyper V 2012 and then just power on the guest VM servers accordingly? Any other possible complications to this at all?  I've just begun testing Hyper V Server 2012  and not too familiar with it, especially in regards to any other possible licensing needs for server OS’s.  My plan is to eventually upgrade the server OS's as well...but want to get them off the end of life physical servers asap first.  Thanks in advance for any input.