Ultimate DOS Archive is a project similar to TOSEC. They collect informations about DOS boot and installation disks. Early versions of MS Windows (up to 3.11) are included. Today a new DATs were released:
DOS - Boot Disks (2010-04-28)
DOS - Operation System (2010-04-28)
You can grab it from the Ultimate DOS Archive site. If you didn't notice yet there are 2 new DATs available in the No-Intro project: Casio - PV-1000 (20100428) and Epoch - Super Cassette Vision (20100428).I'll post the new ROMs soon.