From what I can gather by researching for PCs is that you would have had to have purchased a computer in 2008/09 (Windows XP) or earlier to have an OS that would not support an upgrade to a 64 bit system. If your PC was purchased in 2010 or later it should from everything I've read be able to be switched to 64 bits and for not a lot of expense, depending as far as I can tell on available memory.
It would seem odds are if you were able to purchase and play C&D when those specs changed then you likely will survive this change too. I hope this is reassuring to many, and if I'm incorrect and someone knows better please correct me. :)