me and a friend did a diy rounded cable project for our comps. it was suprisingly easy. we used a pocket knife to cut the cables and bought some rubber tubing and zipties from homedepot for real cheap. we just used the knife to make a small cut into the cable every 5 rivets on ata33 and every 8 rivets or so on ata66/100. after we made the small cut, we just pulled it apart and it split it evenly. needless to say the ata33s and floppy cables were much easier, but just make a good first cut on the hard drive cables and pull them apart and you should be fine. dont be afraid to do it yourself, cause even morons like me can get it right, also if you expose the wire, just wrap it with some tape. total project was 5 bucks and reduced cpu temp by 4C.
oh yeah, you can also use plyers to yank off the middle connector if your not using it. it makes the cable more streamline and easier to hide or strap down. just make sure to tape over the exposed wires where the connector was. im no expert, but everything works fine, so i think its okay.