If Im viewing in one lister contents of the floppy drive I can't use other apps (Like Magic ISO or similar to make a drive image).
If I change the content of lister from floppy to any other drive the lock is gone.
Regards, Raisers
P.S. Oh my... I'm using WinXP Pro on nforce3. 
Opus keeps a shared lock on any device which is showing in a lister so that it can be notified of changes to files and folders on the device. (It does not lock folders, only the root device, regardless of which folder is showing below it.)
If you need to run a program which requires an exclusive lock on a device you just have to close the Opus lister or point it at another place. Programs which only need a shared lock will work fine.
I'm not sure if the same thing is the case with Explorer but I'd be surprised if it isn't, unless MS use a very different way to get change noficiation.
Bit of extra info which is probably not relevant: Programs launched via Opus will also inherit the directory they're launched from as their "current directory", unless configured not to in the button that starts them. For example, if you launch TextPad while in C:\Blah then TextPad itself will hold a lock on C:\Blah preventing it from deletion until TextPad is either closed or moved to another directory, which happens by default if you open a file from another place.