To find the code that you are looking for, go to register.asp and here is the line that requires the e-mail address (lines 112 to 119):
If strAutoLogon <> 1 then
if Request.Form("Email") = "" then
Err_Msg = Err_Msg & "<li>You Must give an email address</li>"
end if
if EmailField(Request.Form("Email")) = 0 then
Err_Msg = Err_Msg & "<li>You Must enter a valid email address</li>"
end if
end if
However, I do not recommend that you delete any of the requirments that comes as a default with the Snitz download especially the E-mail address requirements. The E-mail field is used as a Primary Key field and if you delete this requirements you will end up with duplicate records. But if your intention is to add additional fields to be required, then I do not see any harm in doing that.
Thanks,
Mo