Apparently a common problem but from all the dialogue, no solution that seems to work in my case. I have tried the combinations of power, volume up and home key, power and volume up and power and volume down. With the power and volume up, the machine reboots and then freezes and it is only by chance I found power + volume down used over two cycles allows the machine to close down. Otherwise it just runs down the battery. Plugging the machine into the USB drive I hoped it would be recognised and I could somehow look inside the Tab and see what is there and maybe get to change it, if it is a cache issue. The device had not been used for some time, whether that is relevant or not I don't know. I have had the case open and unplugged the battery before re-connecting some time later so in terms of what the device looks and feels like, I a pretty familiar. it is what is going on inside its tiny (but no doubt powerful) brain that is causing me grief.