post.asp
around line #1059 find the following:
strRqMethod = "Topic" or strRqMethod = "TopicQuote") and strSignatures = "1" and strDSignatures <> "1" then
Response.Write " <font face=""" & strDefaultFontFace & """ size=""" & strDefaultFontSize & """>" & vbNewLine & _
" <input name=""Sig"" type=""checkbox"" value=""yes"" checked>Check here to include your profile signature.<br /></font>" & vbNewLine
end if
replace the red highlighted lines of code with the following: Response.Write " <font face=""" & strDefaultFontFace & """ size=""" & strDefaultFontSize & """>" & vbNewLine
intSigDefault = getSigDefault(MemberID)
Response.Write " <input name=""Sig"" type=""checkbox"" value=""yes""" & chkCheckbox(intSigDefault,1,true) & ">Check here to include your profile signature.<br /></font>" & vbNewLine