No need to fear technology. Just expect some quirks.
You may have to empty the Recycle Bin on your computer to make sure files aren’t left behind.
USB Mode is how the Sansa communicates with the computer. There are two kinds of connection, MSC and MTP. They’re like two different pipelines to the same tank.
In Settings/System Settings/USB Mode you’ll also see Auto Detect, which chooses MTP on Windows computers and MSC on others.
Connecting in MSC mode is like connecting a flash drive, thumb drive or any other USB drive. In MSC, the Sansa looks like two disc drives with separate driveletters: one called SANSA CLIP, one called Removable Drive (which is the microSD slot, and which you should definitely use to put more music on the player).
MTP is a different connection involving Windows Media Player.
Here’s the annoying part: The computer can only recognize material through one pipeline at a time. So if you sent the files by MTP, it has to be in MTP mode. Put it in MTP, look for files, delete them, empty Recycle. Then put it in MSC, find files, delete them and empty Recycle.
Then leave it in MSC mode and look around in there for MTABLE.SYS, which is the listing the Sansa makes of the files. Delete MTABLE.SYS (ignore the Windows warning that it’s a system file–it’s ok to delete it). Make sure you empty Recycle, disconnect and the Sansa will build a new MTABLE.SYS . It may be showing you nonexistent files because it still has the old MTABLE.SYS, but if it’s truly empty, MTABLE.SYS will have nothing to list.
And if stuff still won’t delete…I’m baffled.