Marking a partition as active makes it the drives bootable partition. Each drive can only have one active partition.
Unfortunately, Windows doesn't come with any tools that can resize partitions without first removing the ones that exist. There are good third-party tools that allow you to resize partitions without recreating them. My personal favorite is
Partition Magic. These tools often times cost money, but there are free alternatives. If you really want to use a free alternative, then I'd recommend
NTFSResize. Read the FAQ question "How to resize NTFS without data loss?" for more information.
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