Here's a short patch for InstallOptions that allows you to disable the next button in the same way you can disable the back or cancel buttons.
After applying this patch to installeroptions.cpp, add "NextEnabled=0" to the Settings section of your INI file to disable the next button.
*** installeroptions.cpp.old Sat Jan 31 14:54:46 2004
--- installeroptions.cpp Tue Feb 10 13:12:08 2004
***************
*** 183,188 ****
--- 183,190 ----
int bCancelEnabled = FALSE; // by ORTIM: 13-August-2002
int bCancelShow = FALSE; // by ORTIM: 13-August-2002
+ int bNextEnabled = FALSE; // by nandhp: 10-February-2004
+
int bRTL = FALSE;
FieldType *pFields = NULL;
***************
*** 417,422 ****
--- 419,427 ----
bCancelEnabled = myGetProfileInt("CancelEnabled", -1);
bCancelShow = myGetProfileInt("CancelShow", -1);
+ // by nandhp: 2-February-2004
+ bNextEnabled = myGetProfileInt("NextEnabled", -1);
+
bRTL = myGetProfileInt("RTL", 0);
if (nNumFields > 0) {
***************
*** 888,893 ****
--- 893,899 ----
mySetWindowText(hBackButton,pszBackButtonText);
if (bBackEnabled!=-1) EnableWindow(hBackButton,bBackEnabled);
+ if (bNextEnabled!=-1) EnableWindow(hNextButton,bNextEnabled); // nandhp 10-F
ebruary-2004
if (bCancelEnabled!=-1) EnableWindow(hCancelButton,bCancelEnabled);
if (bCancelShow!=-1) old_cancel_visible=ShowWindow(hCancelButton,bCancelShow
?SW_SHOWNA:SW_HIDE);