replacing spanish characters with the english equivalent

Using vb.net 2005/asp.net
I thought I had the issue solved:  I have some strings with spanish characters such as "ñ" and I need to replace characters with their non-spanish equivalent, ex:  the example I just mentioned would be changed to "n".
My code:
nString = nString.Replace("í", "i") nString = nString.Replace("ó", "o") nString = nString.Replace("ñ", "n") nString = nString.Replace("ú", "u") nString = nString.Replace("é", "e") nString = nString.Replace("á", "a")

when I put a breakpoint I see that usually my code replaces the characters the way that I want and all is good but some replacements are not working well and looking at my breakpoint it appears that there are non-readable characters that are included with ...