System-Partition >7,8GB (it works!)

First I could’nt believe it:
My NT 4.0 SP5 runs on a 13 GB-Partition (Yes only one Partition!)
I formatted the 13GB-Drive in another Machine with NTFS. Then I put the Drive in my old Machine together with a Drive on which I had an Ghost-Image ofmy old Installation. I applied this Image to the 13 GB-Partition and then took out the Drive with the Ghost-Image. And finally I rebooted the Machine. At this point I was sure the Machine of course cannot boot because the System-Partition is greaterthen 7,8 GB, but it works. NT booted and I started Harddisk-Manager to see if this Partition was really 13 GB: and it was.
Now, can anyone explain to me, why this works, altough Microsoft says in Knowledge Base it cannot work ????