I have a USB thumb drive that my computers can read but can't write.
It has a read-only switch, SPDT, but flipping it makes no difference,
nor does unsoldering it and replacing it with a jumper wire. Is there
something else that may work, such as running a special utility (The
manual refers to a "recovery disk," but the driver CD contains no such
thing) or shorting a certain reset pin?.

This device uses an OTI 6828 USB bridge chip and was distributed by
Pretec as the iDisk and also given out by Microsoft years ago (they
have nothing on it), but I can't find any information about it.