of course not!
anyway ... make a backup of the directory where the undeletable file is in ... delete the whole original directory ... create a new dir named (i.e OWB in this case) and copy back all the backuped content BUT the file undeletable.
lol! and now is in the .recycled dir ... impossible to delete it again!
Note- just for correctness.
The above mentioned problem with OBW_OS4, is fixed now.
Performing the Acid3 test with a previous (don't remember now which version), OWB_OS4 tryed to download a file (like empty.xml or so) and crashed leaving that long empty file.