DCS 1.5 Install problem: searching for disk 2

Hi. When trying to install DCS 1.5 the initial part of the install goes fine until I get a message "searching for disk 2". When I try to point it toward the file...l go to the file where it's all downloaded and can't see anything in the file. I'm pretty sure it's just a Windows setting (Win7-64) but I am not computer literate enough to figure it out. If someone would point me in the right direction that would be great. many thanks.

Dave