I'd absolutely go with the newer version, Beginning C# 2005, on the current software version. If for no other reason than you can get the free Visual C# 2005 Express Edition software from Microsoft to learn on. It's close enough to standard Visual C# 2005 that once you are ready to buy a copy of the full software, the transition should be seamless.
Hope this helps.
Senior Acquisitions Editor
Wiley Technology Publishing
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