I just bought a refurbished Dell,I ordered the 64 bit version but they shipped the 32 bit by mistake. I could have returned it at their cost but chose to keep it instead,seeing how it blows away my old x64 because it only had 2 GB of RAM,this has 4GB but a smaller HDD.I have a 350GB HDD on order and need to know if this method will work once I receive it.32 bit is okay but I do some heavy workloads sometimes and play mid level games and a few high end ones,which lag like crazy on my old Laptop!

I have an ISO for Windows 7 x64.If I format this HDD;the new one is blank,if I use this to install I should then have a 64 bit machine,correct?
I realise I may need to install the drivers once it's complete..I don't need all updates only all of SP1 so I may upgrade to windows 10.
If this method will not work,it looks like I'll have to return this PC any way. :/