After the Computer-Name has been changed FROM " ...-PC to ...-ASUS " and Boot-time defragmentation of Diskeeper 2008 started, the system can't boot up to Normal Mode OR Safe Mode. The Monitor got black screen. After the log-on screen show " Windows starting up ", the system start to re-boot again and again and again.

Boot to DVD and try repair. Also re-try chkdsk while on dvd booted. "Best Practices", Event viewer, host file, perfmon, antivirus, anti-spyware, Live CD's, backups, are in my top 10

Thanks Jefro, Befor I posted thise stuff, I have tried what you recommend many many times. But nothing works. I'm sorry. I forget to make sure one more thing, my HDD is newly one. I just bought 40 days ago. I think, the problem cause by this new HDD. The HDD is Seagate, 1TB. Yesterday I ran Seagate Seatools Desktop. the Test result is FAIL. So this is the case? OR any other sources, like VIRUSES, SPYWARES, TROJANS, MALWARES... attacked that cause this problem? As you may know, all HDD are one year under the WARRANTY, but I still want to know the real phenomenon. Your help would be much appreciate.