First of all, I'm new to TechSpot and to posting to forums such as this. However, I've been very impressed with the quality of the various threads I've followed and the usually sincere efforts to assist those in need...such as yours truly. I've worked with computers for years (since the TRS-80 days) and have built several, repaired many and now I'm stumped. My SONY PCV-RZ54G, is equiped with an ASUS P4SD-VL mobo/Intel 3.2GHz P4 +HT, 1gb RAM, 200gb WD 200gb ATA Ultra master + a 300gb Maxtor Diamond 10 slave, Pioneer DVD-RW, DVD-ROM and a Maxtor 300gb One-Touch external drive. After 2.5 years of absolutely flawless performance (mostly Adobe Photoshop, writing and research) the computer started failing to boot going to a black screen with the error "Reboot & select proper boot device or...", you know the rest. This happens on a "cold boot" and after powering down usually starts normally on the 2nd or 3rd try. If I hit F2 and check BIOS settings on a "cold boot", I find that neither internal hard drive has been detected. I've carefully cleaned the computer, removed every cable and card and reinserted to insure clean and secure contact with no luck. My greatest concern is losing my primary HD which is protected using Norton Ghost (I hope). But I'm not able to isolate the problem to either the HD or the MOBO and if it's the MOBO, why is it intermittant? Does anyone know how to properly isolate the probable cause? Thanks for taking the time to read this far. 2 days later: The sunny South turned cool last night...57F with windows open all night and this morning the SONY wouldn't boot at all [20 times - hard drives not detected]. In a burst of inspiration I heated the computer carefully with a small hair dryer and the thing BOOTED FIRST TRY!! Seems to me there may be a cold solder joint or break somewhere. Any ideas would help.