according to this link ftp://ftp.dell.com/Manuals/all-products/esuprt_desktop/esuprt_dimension_desktops/dimension-4600_service%20manual_en-us.pdf you also have 2 sata ports on the motherboard.will need a sata data cable & most likely a sata power connector adapter if current psu does not have a sata connector on it.

You can also buy an expansion SATA card that will plug into your motherboard if your other SATA ports are already used.

go to www.amazon.com and purchase an ide to sata or sata to ide adapter this comes with power connector and ide lead for approx £3.30 incl post and packing this should cure your problem