clean install with upgrade DOWNLOADED

i am planning to buy the upgrade version of win7 (i have genuine vista) but im planning on buy it online from the microsoft store, i read the clean install from upgrade sticky but i noticed this; ' This will show you how to do a Clean Install using a retail Upgrade Windows 7 installation disc.'

I notice the words 'retail' and 'disc' i am wondering if i download the official version is that considered retail? and im not really sure how it works, i have never downloaded an OS before, do i need to burn it to a disk once its downloaded?

If so will it then work like the regular disk allowing me to do what the sticky then goes on to explain, or will it know its my home made 50cent disk and think my copy is fake?

Sorry if this has been asked before, i did a search but couldnt find the answer to this, also i hope im being clear i dont know how else to explain. I admit fully to being noob.

I am downloading it, i will not be given a disk.

Of course i will follow the instructions, but id like to know BEFORE i pay for it, if i wont be able to do the clean install from a burned copy.

Can anyone tell me?

thankyou for that info. i am downloading it now, i will be sure to burn slowly. I also like your sig :)