I have noticed that the combination of NOD32 3 (latest build 621) and Diskeeper 2008 Professional on Win XP Pro causes irrepairable corruptions of the volume bitmap that simply cannot be fixed, even after removing both suspected offenders. Has anyone else experienced this? Since I noticed the problems only after updating NOD32, I wonder whether NOD32 might not be the problem. I have now seen the identical hard drive problem on two completely different systems that previously never had any issues (I run chkdsk and perform backups on a regular weekly basis). On both systems, I returned the hard drives to the factory state after a physical reformat several times and the problems repeatedly recurred with these two programs. When I first noticed this on my laptop, the problem was so perplexing that Lenovo recommended sending in the laptop for repair of suspected hard drive or controller defects (and I have not yet received it back). Subsequently, I rebuild my desktop PC from scratch using factory CD's and I installed these two programs after running all OS and manufacturer updates, and boom, the identical problem occurred again. Now every time I run chkdsk, it recovers lost files, discovers free space marked as allocated in the master file table (MFT) and volume bitmaps, and problems with the file system. Oddly enough, running chkdsk /F at boot time does not find any problems. Using a Symantec Recovery CD to boot, Norton Disc Doctor finds problems that it claims to fix with the security descriptors (which by the way do not show in the report). All system tests with PC Doctor, and memory tests pass without indicating any hardware errors. Having the same error on two systems leads me to believe that it must be either NOD32 b621 or Diskeeper. However, the combination of Diskeeper (same version) with NOD32 b621's predecessor did not produce any problems. Any advise, help, pointers would be greatly appreciated. Thanks.