@wean_irdeh
The quote you made of cdob's post does NOT mention anywhere a (fd0).
So not only you are not following Steve6375's tutorial , but not even cdob's ones.
The image you posted a link to has these characteristics:
1) it is a partitioned hard disk image (good)
2) the only partition (NON active) starts 0/2/3 and ends 2/174/44, LBA 128, 43008 sectors
3) its PBR has geometry 255/63
4) as grub4dos told you, you have excess sectors after the end of the partition (you should have just one, the VHD footer) (128+43008)=43136*512=22,085,632
5) and BTW it is NOT 50Mb in size, it is (exactly) 25,166,336 bytes
On most BIOSes (including evidently the Virtualbox one) such a small device won't have a 255/63 geometry, you may need to pass the cylinders and sectors parameters to grub4dos to mount it, but what is the point? (you should NOT map the partition to a floppy device anyway).
Wonko