Why is the 5th string on a guitar tuned to B and not C.

http://stuffo.howstuffworks.com/guitar2.htm

This site goes into a very detailed explanation of tones/frequencies,
and how each string's tuning is calculated.  There is an intro and one
page prior to the page above, but I believe what you're asking is
covered on the page given.

I'm not sure it will answer your question completely, but I'm sure it
will shed some light on your dilemma.  :)

This subject appears to have been frequently discussed in newsgroups
of guitar aficionados, with no consensus being reached.  Here, from
rec.music.guitar.acoustic is an interesting posting on the subject:

"Why EADGBE? 
The rec.music.classical.guitar newsgroup discussed that rece­ntly, but 
did not reach consensus. :) 

"EADGBE became the predominant tuning for six-string guitar t­oward the 
end of the 1700s.  That tuning extends the ADGBE tuning of t­he Baroque 
guitar, which had five double courses (ten strings).  Before­ that, the 
four-course Renaissance guitar was tuned DGBE or some transp­osition 
such as CFAD.  The vihuela's six double courses were tuned E­ADF#BE. 
In the sixteenth century, the lute's top six strings were us­ually 
tuned GCFADF, which is a minor third higher than the vihuela­ tuning. 

"There were many exceptions to these generalizations, and man­y other 
tunings and instruments in common use.  This history doesn't­ really 
explain anything, but it helps to show that so-called standa­rd tuning 
is, like the six-string guitar itself, a fairly modern conve­ntion." 


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