Hi all, thanks in advance for reading! I've been experiencing these issues since I began my foray into Windows 7 over a week ago. Before I describe the issues, here's my system's stats: Asus P5N-D 2x2gb Corsair xms2 DDR2 800 @ stock C2D E8400 @ stock nvidia geforce 8800 gts 1 x WD Raptor 37gb sata 1 x WD Caviar 250gb sata 2 x Samsung Spinpoint F1 750gb sata During large file operations (moving, copying/pasting etc) between HDD's of items (single files or groups of files and folders, and from the Caviar to either Samsung) exceeding several gb's worth, the system would hard lock - no mouse/keyboard, all visual progress halted, no visual HDD activity. If left alone, the system would very intermittently flash a black display and return to the frozen desktop display, eventually winking out to a total lack of display output altogether. Upon soft reboot, the destination HDD has been dropped from BIOS, boot menu, etc. Boot hangs at midpoint during the splash. Hard power-cycling yields the HDD reappearing and Windows starts without issues. What I've done so far: -Disconnected destination HDD and tried the other spinpoint, same result. -Diag'd all HDD's with manufacturers' tools, all pass. -Flashed BIOS to most recent update, no change. -Swapped out the WD Raptor for a freshly unboxed WD 640gb Caviar Black. Clean installed W7 x64 after format etc and did NOTHING (this means installed no drivers, no programs, nada) but attempt the file operations after first startup post-install. Same issues. (Sidenote - after power-cycling, W7 booted without Aero and threw up 'access denied' sorts of errors when trying to access anything within the start menu, desktop context menus, etc. Will attempt a second fresh install after sleeping a while.) I should also mention that these crashes do not generate entries in the event viewer system log - only 'unexpected shutdown' entries from me power-cycling the damn thing. I know other users have had similar issues with HDD drops, and some have had luck bumping BIOS voltages a bit but I see no reason that should be necessary given what I've got under the hood. I also should mention the md5 hash checks out on the iso image from MSDN, I made sure of this after getting a bum image the first time around. A few final notes: I have considered the possibility of bunk SATA controller drivers, but for one I've read of others having similar issues, and updating said drivers to no avail, and for two I was running winXP x64 (100% updated) perfectly on the very same hardware mere hours prior. As for RAM instability, memtest86 on my xp x64 system ran flawless & system was prime95 stable for hours on end. I haven't attempted stress testing yet as I don't believe this is a hardware issue. Thoughts? Sorry for the long post, but good explanations of details always help!