Download problems 64bit windows 7...please help

I had some mac trouble with white screening...with apple care we wiped the system and installed a new machine running the latest OS. I have parallels 8 and gone out and bought windows 7 professional...I have two options 32bit and 64...I need to install the 64bit for my software...now it gets to about 15% and then my mac white screens. I installed 32bit just to test it out with no bother at all...would someone please help Before I rush out and do something foolish like buy a new mac...my business has ground to a halt.
many thanks in advance
Cheryl