It will not be necessary to download the software again. You only need a flash/pen drive with more than enough free space to accommodate the contents of the disc.
Insert the disc into your computer and also insert the flash drive.
Now , go to my computer and right click on the cd.
Select the copy option.
Then , go to your flash drive and right click on a free space and select paste.
This will now copy the contents of the disc onto the flash drive in a folder names after the cd.
Not simply remove the flash drive , put it in your laptop and go to the correct folder. Then open the folder and look for a file names Autorun which will normally have a little setup icon.This will start the setup.
If you can't find the autorun file , there should be a setup file which you can run and it will also install the software.
You will be able to use you serial as normal but please be advised that unless the product is licensed for more than two computers , this process is technically illegal.
Please let me know if you need some more help or info.