downgrade rights question

You must use Dell Windows 7 OEM System Locked Preinstallation. See here for details:

http://dellwindowsreinstallationguide.com/downgrade-rights/

so i don't need a windows 7 pro key I can just use a dell brand cd

latitude E5470

We need to know what model the new computer is exactly. Give us the details:

http://dellwindowsreinstallationguide.com/uefi/

Likely however you'll need USB 3.0 support and NVMe support. See here for details:

http://dellwindowsreinstallationguide.com/windows-7-sp1-iso-download/

Okay I have check with the new computer supports windows 7 and it does ,will the disc work on my computer if there drivers for the computer

Looking at the specification you'll definitely need to use the updated installation media:

http://www.dell.com/uk/business/p/latitude-e5470-laptop/pd

Hi where do i get the update media from

See the instructions here. You may be able to download it after inputting your service tag:

http://dellwindowsreinstallationguide.com/windows-7-sp1-iso-download/

Hi can I use a usb 3.0 dvd drive for the windows 7 installer ? will it pick it up

Only if you use the updated installation media. Earlier installation media lacks USB 3.0 support.

Hi which update media do i need one with sp1 one ? thanks

You need media with "SP2" otherwise know as the convenience rollup, NVMe support and USB3.0 support...

where can i find an iso image of sp2

See here:

http://dellwindowsreinstallationguide.com/windows-7-sp1-iso-download/

It discusses the updated SP2 images below the SP1 download...