Clean install of Windows

My laptop came with Windows Vista 64 bit, not knowing the ram limitation, I downloaded and installed Windows 7 32 bit. I want to go back to 64 bit vista, but I found out the only way to go from 32 bit to 64 bit is to do a clean install, and that I can't just boot it on a virtual disk. If I burn the Windows software onto a blank DVD, and install it like that, will it work as a clean install?

 

Yes, but only if you boot from the DVD and repartition.

 

I downloaded windows xp home edition for my computer because it's broken won't even go to the login page so some one told me I have to install windows on it again so i downloaded it on my laptop and tryed burning it onto a normal disk but it said error or something.