I have an ASUS P6T with an i7 920. My primary drive is an older WD 160GB on the IDE controller while my data drive is a WD 1TB SATA. I'm using Windows 7 (but that should be moot for this question).
The rig has run just fine for a year now, but recently upon rebooting, the JMicron controller is no longer detecting the IDE drive (and is thus not able to load the OS). As I troubleshot, it randomly picked up the drive again during a reboot and started up Windows with no problem. I moved my PC back to my office, started up again, and once again there was no IDE.
I've updated the Bios, played around with disabling Express Gate and a few other various Bios settings that I've heard might work, but nothing seems able to bring back the drive.
I would use your motherboard cd and load the Intel chipset driver, which should contain the jmicron driver. If you don't have the cd, download the driver off asus website. Also try changing cables and reseat all connections, including the power supply leads.
Good suggestion, but unfortunately no joy... I did a full integrity check of all connections and restored and upgraded the BIOS.
I'm starting to think it may be the HDD itself - I tried firing up an old rig with it in and it went undetected there as well. If I can just find another IDE sitting around, I'll see if I can get the newer rig to see that one and that should isolate the component.