It just can't get simpler than that:
#include <GUIConstants.au3>
$MainGUI = GUICreate("INI Stuff", 202, 95, -1, -1)
$Input = GUICtrlCreateInput("", 8, 8, 185, 21)
$Clear = GUICtrlCreateButton ("Clear Input's Data", 8, 36, 185, 25)
$IniWrite = GUICtrlCreateButton("Ini Write", 8, 65, 57, 25, 0)
$IniRead = GUICtrlCreateButton("Ini Read", 72, 65, 57, 25, 0)
$IniDelete = GUICtrlCreateButton("Ini Delete", 136, 65, 57, 25, 0)
GUISetState(@SW_SHOW)
While 1
$msg = GUIGetMsg()
Switch $msg
Case $GUI_EVENT_CLOSE
Exit
Case $IniWrite
IniWrite ("Ini File.ini", "Input Section", "Input Info", GUICtrlRead($Input))
Case $IniRead
GUICtrlSetData ($Input, IniRead ("Ini File.ini", "Input Section", "Input Info", ""))
Case $IniDelete
IniDelete ("Ini File.ini", "Input Section", "Input Info")
Case $Clear
GUICtrlSetData ($Input, "")
EndSwitch
WEnd