That 5.1.2600 string is the operating system version I would presume. XP is Windows NT v5.1 build 2600. Windows 7 shows format.com as 6.1.7127.0. Again, Windows NT v6.1 build 7127.
The version comes after that and shows 0 which doesn't make a lot of sense. In XP it shows as 5.1.2600.5512 so I would presume that format.com is version 5512.
If you open Windows 7 format.com in a text editor you get this...
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<!-- Copyright (c) Microsoft Corporation -->
<assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0">
<assemblyIdentity
version="5.1.0.0"
processorArchitecture="x86"
name="Microsoft.Windows.FileSystem.Format"
type="win32"
/>
<description>Disk Format Utility</description>
So a lower version?
When I have some time, I'll format a spare drive with both and see if there's any speed difference while moving/copying files that I can measure.