There is a desk top computer and a cat is sitting next to it
A cat is sitting on a desk next to a computer monitor.
A computer desk with a cat laying on it
A cat that is laying on a computer desk next to the monitor.
A desk contianing a computer monitor, telephone, modem, CD drive, and a cat above a keyboard drawer containing a keyboard and a mouse which is above a tangle of wires and next to a bed.