We occasionally see machines that either freeze on booting or constantly reboot AND (here are the specific symptoms) ALWAYS, when we run chkdsk fron the recovery console give the message "CHKDSK is performing additional checking or repair.." three times in a row (never more or less - always three times), then hangs at 25% for a while, then proceeds (intermittently slowly) to 100%. When re-run, chkdsk gives the VERY SAME result, time after time after time. We have never found any fix except format and re-install. Has anyone else seen this? Do you have any better fix for it?