Answer to: memory low mesage but disk is clearMemory is Memory, storage space is not memory, this may be a case of a failing RAM Chip like @phudson38 eluded to (but let me expand) I would shoot for a new stick of RAM (what windows OS are you using?) if you have a 64 bit version go for 8 GB
Answer to: Can not view pictures, storadge space is running outI would suggest if you (only copied the files) to reconnect the Tab to the PC and "navigate" to the media folders and delete the files manually. Also as long as you are sure you copied said files.... I'd like to venture a guess a "factory restore" may be of some help. Don't worry, if you have paid apps on there you can still get them back.