If you can put files away, I'd suggest you delete any volumes on your drive from Disk Management, create 3 500GB new partitions and copy files back.
Unless you require FAT32 for compatibility purposes, I'd suggest you create your volumes as NTFS (it will ask you when creating partitions). It is more resilient against file errors, and supports file sizes larger than 4GB.
Once volumes have been deleted, follow this procedure (more info here):
Right-click an unallocated region on your hard disk, and then click
New Simple Volume.
In the New Simple Volume Wizard, click Next.
Type the size of the volume you want to create in megabytes (MB, so ~5000000 for 500GB) or accept the maximum default size, and then click Next.
Accept the default drive letter or choose a different drive letter
to identify the partition, and then click Next. (you can always change the letter later)
In the Format Partition dialog box, select "quick formatting" and format the drive. Leave the allocation unit size at default, and you can give a label name too. I don't recommended file and folder compression.
Repeat for other volumes in the unallocated space.