Mapped drives bootup login failer

I have a problem to find a solution for. The small office has a few PCs that map a drive on on local machine. They are mapped fine and can browse the folders contained inside. The problem is that on booting some of the machines connect automatically to the networked drive. Some machines do not. Then only connect after the share is clicked for access in explorer. The problem with that is there is software that needs that drive, and it cannot work until the connection is made. All machines have reconnect at login box checked. I would like to know if anyone has had this problem before, and thier solution. Thanks jeff