I think before you start jumping to re-partitioning and loading Operating systems... you need a little research on what type of applications you are going to need to run for your business, and check their compatibility with a) VISTA b) 64bit VISTA
I like your blog, so you need to see if Microsoft have 64bit versions of Visual Studio 2005 / 2008, SQL Servers, Office etc etc... I think the 32bit versions will run, but will be in compatibiltiy mode which might slow you down.
Also, the supposed advantages of 64bit, is the extra addressable ram allocation i.e. Greater than 4GB... depends if you are going to need that much, or if you plan to develop 64bit apps?!
Out of all this, Vista will allow you to do most things (albeit slower compared to XP)

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