This one has me really pulling my hair out, so any help would be appreciated. I recently purchased an Intel i7-3770k processor and motherboard (Gigabyte GA-Z77X-D3H) to replace my aging AMD PII 1100T/790FX MB setup. The upgrade apparently did went fine and I used my old Windows image after scrubbing it of the old motherboard's drivers. It basically ran fine, but I had a problem with some of my HDD "disappearing" randomly in Windows or in BIOS, and occasionally hanging on post. This happens regardless of how the drives were connected (internal SATA, eSATA or USB3) and with different drives (a PNY SSD, Seagate Barracuda 3TB, WD Scorpio 750GB, etc) I did a clean install of Windows 7 thinking it was some driver weirdness, but the same thing is happening, and even more distressing is the machine often times will just hang in POST (never gets beyond the splash screen) or those drives will not appear in BIOS. The problem is very intermittent, but since it is happening despite what I have the drives connected to (SATA, eSATA, or USB3) I'm wondering if the southbridge has a problem. The BIOS is set at all the defaults (ACHI and no overclocking) and has the newest BIOS update. Any thoughts?