Your anchors aren't set correctly. You're gonna have to muscle through this yourself. It's going to require you to make a change, and then test it out.
EDIT ==============
In response to your comment - if it still doesn't work, you still aren't doing it right. Try this explanation of WinForms anchors:
http://www.techrepublic.com/article/manage-winform-controls-using-the-anchor-and-dock-properties/6165908[
^]
If that's not enough, google is your friend (I googled "designer control anchors" to find the link above).