External Hard Drive Not Opening on one Computer but Opens on another?

You cannot create a fat32 partition larger than 32GB on windows. If you want to use windows for it you will just have to create several 32GB fat32 partitions on it so that you can use it on your xbox. The only way that I have been able to create a fat32 partition larger than 32GB is by using ubuntu linux. I have used this method many times on my 1tb external hdd to back up my ps3 and it works perfectly.