|>> I only have 435 MB available to make into a separate partition, but my hard drive has 222 GB free out of 298 GB total. <<|
Is this free space or unallocated space. There is a difference. Free space is space that has been partitioned and formatted but not used. Unallocated space is space that has been neither partitioned or formatted. You need unallocated space in order to create a partition.
It appears you have 436 Mb of unallocated space and 222 Gb of free space. To convert some of that free space into unallocated space shrinking is what you need to do. So what error message to do get when you try to shrink the existing partition.
It may be that it is only allowing you to reclaim 435 Mbs of the 222 Gbs that is free. This often happens if the drive is badly fragmented. So I would suggest defragmenting the drive and try again.
>> I didn't know you could partition a drive from Disk management. <<
Windows XP has had the ability to partition a drive from day one. Windows Vista has the added ability to shrink a drive which previously would have to be done by a third party utility like Partition Manager.