You can't "upgrade" your 32 bit system to 64 bit. You need to clean install, and format your drive/partition on the way with the windows 10 64 bit DVD you'll boot from.
Make sure you image your current system using Macrium Reflect or similar, so you can revert to your current system if you need to.
You can always download a 32 bit ISO file if you ever need one.
Short answer to your question is, "no, if something goes wrong your system won't revert back to 32 bit because you'll be formatting that partition".
12-17-2015 10:41 PM