Entity Selection

[Jabba]

I am using AutoCAD 2000 and have suddenly come across a problem I cannot solve. When I try to select a number of objects within a selection set, say four lines, I can select the first one then when I select the second one, the first becomes deselected! When I select the third one, the second becomes deselected and when I select the fourth the third becomes deselected therefore leaving me with the last one in the selection set!
Im sure its a setup variable that needs changing, but I cannot fins which one it is. Can anyone help?

[fuccaro]

After you select the first entity, hold down the SHIFT key and than select the others. If you don’t wish to work in this way, then you may change it. Go to TOOLS > OPTIONS > SELECTIONS. Probable the option USE SHIFT TO ADD TO SELECTION is checked.
And I have more a very important thing to tell you: welcome to the forum Jabba!