I never tried to do this, but I think once the partition information is on the disk that LVM and OS2DASD will just use it. You have to erase that. I'm not sure what other OS/2 utility can do that, but DFSee should be able to clean that stuff out. If you don't want to use DFSee, then try all the OS/2 utilities to wipe the partitions and MBR info.
lvm /newmbr might do it.....