This is fairly long, but please read it entirely as it's all relevant. In January I installed a new mobo and did a fresh install of XP x64. Back in June or July, I started using AppDefend beta for x64 and like it enough to buy the site license (to cover my computer at work as well as at home). Within the past month or two, I've started noticing hard locks with my system that seemed to happen whenever there was HDD activity, leading me to question if my HDD was going bad. I rebooted into the Recovery Console at one point and ran chkdsk and it found fixable errors on the drive. That futher increased my worries that the drive might be failing. I was also having issues with another program I use (Alcohol 120), so I decided to format and reinstall. Friday night, I wiped the drive and did a full (not quick) format on the HDD. After reinstalling, I started going through the usual motions installing all my necessary software. I finally installed AppDefend (well, Ghostwall actually as AD isn't available seperately for x64, but RD is disabled). I rebooted and then updated AD and rebooted again. After reboot, I installed PowerDVD 7. But my computer locked up while trying to install it. It would lockup while browsing websites with Opera, too. Now seriously concerned about the state of my HDD, I rebooted and tried extracting Memtest86+ from a self-extracting exe, but it locked up while copying it to the desktop. After a reboot, I created a disk of Ontrack Data Advisor and rebooted. I scanned my HDD for errors, but after a half-hour or so of surface scanning, it came up clean. At this point I had been wondering about AD (as it's the last thing I installed before the lockups began again), but I dismissed it as all the signs seemed to point to HDD failure. But on a whim, I rebooted and uninstalled AD. After another reboot, I haven't encountered any more hardlocks. I will be monitoring the situation over the next few weeks to be sure, but it's looking like something with AD was causing my system to hard lock itself. The only thing responding was the mouse, and sometimes the open windows could be moved (but not closed). Does anyone have any thoughts on this issue? Has this been seen before? Since formatting and reloading, I haven't even had a chance to install the Windows updates before the system started locking up, so it can't be a conflict with the udpates. I do realize this is long, but I appreciate anyone who has read this far and hope someone has an idea for me as I'd prefer to keep AD on my system. Thanks.