If I want a sentence clear of any doubt then it has to be number 1 in your examples. In your examples you have cleverly chosen items that are linked, e.g. Tape and Disk Drives, along with other references around the same topic. In your second

I would always use a COMMA before AND unless the last 2 items are related. For example, 1, 2, 3 and 4, would suggest 3 and 4 are coupled. 1, 2, 3, and 4 provides an absolute definition suggesting that the 3 and the 4 are seperate entities, which