How to Install Windows on a New Rig with Old HDD..yeah

Ok, so I've ALWAYS been confused about this point in any sort of comp build and I want to ask this question to clear this all up.

My friend currently has a Frankenstein of a rig with a Gateway mobo with Win7.on the HDD

And for an upgrade we are looking to get a new mobo+cpu, etc.

I want to know ask is if this procedure is correct, if not please inform me:

I would get the new parts, put everything together, I have a flash drive set up to boot with an iso(that matches my current one in the HDD) i downloaded form digitalriver.

Mash on an F key, boot with flash device, then enter the serial number on the OEM CD case, OR use windows loader.

 

Is this right?

Thanks in advance

 

If don't change the hard drive then you do not need to do anything with Windows. Just put the new parts in and it should boot up.

enjoy thou many errors thou shalst encounter

Memory upgrade : nothing needed

GPU upgrade : remove old GPU driver/install new driver

PSU/Optical Drive/Case : nothing needed

Motherboard!!!!!!!!!! fresh install for gods sake :D