How to create image of an MSX diskette?

What kind of disk (file based/sector based)?
Do you have a compact flash card/sd card/physical disk only?

Try 'Disk manager' From Lex Lechz.

Link: http://www.lexlechz.at/en/software.html

I tried a few times to create a new disk image with diskmanager. I probably was wasted, cuz I couldn't get it done. Instead I made a copy of an existing DSK file and just formatted that one. Keep that in mind if you can't get it done either

Needless to say, you need a pc with a 3.5" FDD. USB FDD is an option, but they're mostly of inferior quality.

Thanks for all the answers.

That doesn't seem to be as difficult as it seemed reading other threads. anything to be cautious about? I know that it needs to be write protected so that windows can't write on. Problem I don't have the disk with me, I have to tell my brother who lives thousands miles away how to do it and send me the image. are usb disk drives safe or just might not work? I have to be sure, obviously this is the only copy in the world

As long as it's set to write protected you can try any drive. You said it's a 720kB disk, so it's double sided. That immensely increases the chances that an USB FDD will be able to read it.