I once (long time ago) experiment to create All In One DVD contain multitude Windows, Linux Live Distro, OpenBSD, FreeDOS and several odds like Mikrotik, QNX NC etc. All cramped in single DVD and of course it works. Today, OS is getting bigger and giganteous not to mention excessive during the adoption of DVD standard.
The basic multiboot CD/DVD is to have bootloader that chain another bootimage file. I'll take isolinux for this guide, simply because it's open source and customizable. This method as I mention previously is not limited to Ubuntu + Windows 7 it could be (almost) anything.
7Zip, If you have ISO images
1. Do we have isolinux?
Chance is if you have Ubuntu DVD/ISO then you already have it, look for "isolinux" folder. Just note this..
2. Dump Ubuntus ISO Images into empty folder say "D:\ISO\RemixDVD"
Use 7zip to extract the file or if you only have DVD just copy all files.
3. Dump Windows 7 ISO Images into same folder above using the same method.
4. Find the bootloader of Windows 7
I'll cover this maybe in separate post but for now it is "etfsboot.com" under "boot" directory. Copy this file into isolinux folder and rename it to 7.bin (in isolinux, all bootloader must be explicitly in *.bin files)
5. Delete any [Boot] folder under "D:\ISO\RemixDVD" in this case we don't need them.
6. Edit Isolinux's Boot Menu File
The file is text.cfg (although varied among distros) under isolinux folder. Open it with notepad and append following lines:
menu label Install Windows 7 32-bit
6. Fire up CDRTFE
Drag and Drop all files under "D:\ISO\RemixDVD" into CDRTFE's explorer
7. Press "Filesystem" Button
Make sure no addtional filesystem checked except UDF (this was explicitly needed since Windows 7). Check "Create Boot CD", "Hide boot image", "Hide boot catalog", "No disk emulation", "Create boot info table" then browse file for boot image, use isolinux.bin under isolinux folder. In ISO9660 tab check ISO Level=4 and uncheck anything else. Ok
8. Burn it...
In case you want to test it first, press CD Options select "Use Image", define where to save the ISO file and check "Create image only.."
9. Test it under VM like VMware, VirtualPC or VirtualBox if unsure
10. Optionally if you want to change boot menu logo, feel free to change splash.png under isolinux folder.
due to exclusiveness of Ubuntu's isolinux, it will run Windows 7 bootloader in background thus if your system already have active OS installed you need to press Enter twice, one to select and other one to dismiss question "do you want to boot from cd/dvd"