Revisiting my earlier comment, the Dell Inspiron 620 may have a proprietary front panel, but the pins themselves are standard Molex and thus generic case connectors will fit them. The two LEDs (HDD Activity and Power) are in the usual positions, but the power switch pins straddle the header, with one pin on each side.
Recently, I moved a Dell XPS 8500 motherboard acquired on eBay into a Cooler Master N200 case and although the front panel header is proprietary as just described, it was still compatible with generic connectors.