a 3.9 gig file isn't burnable, how do i download these as 2 gig files or smaller

Unfortunately you can't. There is no download offered with smaller files.

However, what you can do is burning a disk in Universal Disk Format (UDF) and not the old standard ISO 9660. The 2 GB file size limit only applies to the latter, while no modern operating system will have problems reading disks written in UDF. All you have to figure out is how to change the settings in your DVD burning software.

Most of the newer CD/DVD burners set the format automatically. CDBurner XP doesn't even ask it, just do the job. Since it is free, I recommend using that.