Set the Check status of each RadioButton in the
Form_Load
event
rbOne.Checked = False
or
rbOne.CheckState = CheckState.Unchecked
.
Although I haven't been in this situation, there is a possibility that the IDE will automatically assume that at least one of the RadioButtons should be Checked since they are all grouped together in a single control, in this case a GroupBox.
The "Tab Index" controls only the Tab sequence - the order in which the cursor will jump from one control to the next when the TAB key is pressed. However I am not sure if it will determine if a RadioButton should be checked or not.