If your Windows 7 DVD doesn't bootup from you DVD write/rom even though you have changed the BIOS setting to boot from CD/DVD then there may be something wrong or corrupt on you bootmgr of you Windows CD.
To over come this situation you can start your installation of the Windows 7 from a bootup/repair disk. Instructions on how to create a bootup/repair disk click here.
After you have created your bootup disk follow the below instructions:
1. Change the BIOS settings to boot from CD/DVD
2. Enter the BIOS by pressing DEL key at the startup of you computer
3. Go to Boot or Advanced BIOS features
4. Change the First Boot Device to CDROM or DVDROM
5. Change the Second Boot Device to Hard Disk
6. Exit and Save the BIOS setting by pressing F10
*Note the above instruction are for generic PCs which are normally similar setting
7. Power up the PC
8. Insert the Bootup/Repair disk in the DVD
9. At the black screen you will see a prompt "Press any key to boot from CD or DVD.."
10. Immediate press Enter or any other key
11. Follow the prompt to till you reach System Recovery Options window
12. On the first window that appear select "Use recovert tools that can help fix problems starting Windows."
13. On the next window Click on the Command Prompt
14. In the command prompt take out the bootup/repair disk and replace it with the Windows 7 installtion disk
enter the folowing commands:
x:\sources>cd /d F: [press enter, where F: drive is your DVD writer/rom drive]
F:\dir [press enter, this will list all files and folders in root directory of F:]
F:\setup.exe [press enter, this will start your Windows 7 installation]
*Note if you can not find the DVD drive, then try the following commands:
x:\sources>cd..
x:\dir [you should see setup.exe listed]
x:\setup.exe [press enter, this will start your Windows 7 installation]
Follow the instructions to complete Windows 7 installtion.