The rotating disk pictured is a HD disk. It has a square hole on each of its top corners. A DD disk has only one hole on one side and is closed to write protect the disk. Some embroidery machines read only a DD disk. But DD disks are no longer in great supply and some daring folks have gone so far as taping up the hole on a HD Disk, assuming this will work just fine.  Although this is a great emergency solution, it shouldn't be considered a permanent one. In the embroidery industry, losing data -- especially in the middle of a run -- is not something anyone wants to chance.  But if you're still intent on taping up the hole on a HD disk, read on.
 

"CAN I COVER UP THE HOLE WITH TAPE AND FORMAT IT 720K?" "No, no, no, no!!! Bad advice,"claims Ross Wright, media professional.  "Why?  You stand a great chance of loss of data." "High density disks are actually *half* as sensitive as DD disks. Since DD disks are more sensitive than HD disks, when you format a HD disk in DD format you are actually placing a recording on the disk at nearly twice the signal strength that it was designed for.  Granted, you can perform this operation, and even write files to the disk. But eventually the magnetic domains WILL interact and result in data loss - which could take days or even months." "If your machine manufacturers say use DD, and the manufacturers of the floppies are telling you to use DD, and people are telling us they lose data on HD disks formatted to DD then it's only logical to USE DOUBLE DENSITY FLOPPIES!!!"

So you see, folks, it might work for awhile, but you are taking a big chance. The havoc could occur and cause immediate shut down at the most inconvenient moment.  But if you need more convincing, read the following posting from an e-mail embroidery discussion list:

"I've found some of the machines do not handle the HD when formatted as DD (even if opening is taped). The particle size of the magnetic media is different, and can cause mis-read errors. I've used HD in a pinch, but have had a couple come back because the customer's machine could not read it. So I always try and use the proper density disk. If you are using a PC for the reading and then networking into the machine, then no problem usually. As the PC systems drives can usually read both HD and DD disks. Whereas, the machines that have built-in readers usually can only read the DD disks (especially those made late 80's early 90's). We use a ton of HD disks, but we also use a ton of DD disks in our operation, and are finding it harder to locate the DD in quantity. The price between the two is about the same, so for internal storage we always use HD disks. But when we ship a design in either Barudan or Tajima formats we always use DD disks.  EXCEPT when the Tajima file is going to be read on a Brother system, then it must be on a HD disk. (One more wrinkle we have to remember.) It took a long time for the industry to move away from paper tape (we get requests, and can still do them), so I imagine it will be a while for the factories to pay to retrofit their machines to read HD disks as standard."