Cannot write to diskette under Windows 7

Using the Boot-US bootloader installer, I selected the option to write the boot menu to diskette, but this repeatedly fails:

"Writing sectors to Diskette A: failed
System message: Access is denied
Install of Boot Manager failed."

I formatted the diskettes (tried 4 different diskettes) - both 'Quick
Format' and 'Format MS-DOS system disk' - but to no avail.

I tried calling the installer 'as Administrator' (although I am the only user on the system, and have Administrator privileges).

No problem formatting the diskette (which is NOT write protected), or writing to the diskette using other operating systems.

Can anyone suggest what is blocking the write, please?

> Can anyone suggest what is blocking the write, please?

P.S. Wordpad had no problem writing a test file to the diskette.
I checked it was there, then deleted it. No problem...

But the Boot-US installer still gets "Access denied" - even when I call it as Administrator.

The developer of Boot-US has found a bug in the code, and has (on a Sunday evening!) uploaded a revised package (2.1.8), which I have now installed and which now succeeds in writing the diskette!

End of story...