vtar is closed source (right?, wrong?), so there is not win32 port of it
Normal tar format aligns files on 512 byte boundary. vmtar does it on a 4K (page size) boundary. This helps sharing pages for running apps directly with the vmtar file. Otherwise, we would need to allocate memory. So for example, if you have 10 apps sharing a page, the memory needed is 1 page. But if we were to allocate, then it would be 10 pages.
vmtar is internal only and the following is not officially supported
You can get vmtar from /sbin/vmtar after you boot the machine.
.vib itself can be opened with 7-zip (but not saved)
vSphere Installation Bundle
How to create your own .vib files - Yellow Bricks
But the "solution" is really old & here
Convert .vtar to .shar & then extract!