Going to run a couple of Instances of MT4 on a server, any drawbacks with Windows Server 2003?

 

Or should I go with 2008?  Or for all intents and purposes is there no difference?  I can see running up to 6 instances at the same time but as my budget is small I am looking at a used entry level setup.  I need more consistent uptime than my laptop allows for a host of reasons. 

Reason: