You don't need to format your drive.
In Partition magic, you can resize your drive so it's smaller, and then it the rest of that data that you trimmed off becomes 'unallocated data', and you can right-click that and create a new logical partition.
I'm not exactly sure about the page file size now, after reading catfish's post.
Why exactly do you want it to be the same size, and not a range?