Hi! Please help me! Whole story (not really needed, find specific questions below) One day my WinXP didn't boot, there were missing files and it asked me to use the instalation CD to load the recovery console or something. But the CD didn't detect the hard drive, a message "Press F6 to install SCSI or... " was displayed for a few seconds and then nothing, no further response from the system. Tried many times restarting the PC but with no different result. Having Norton Antivirus always updated and being always very careful with all those matters, I never imagined that my problem was a virus. The hard disk was very old and I thought that was a good reason for the boot sector to fail. So I installed a new hard disk as master and the old one as slave. The installation CD detected the new hard disk and ran properly. I made two partitions, I installed WinXP in the first and copied my files (from the old hard disk) to the second partition. I checked both disks with Norton Antivirus and ScanDisk and found nothing wrong. I wanted to use the old hard disk to backup my files every day, so I made it FAT32 to be able to access it while booting from a Win98-made MS-DOS disk, in case of disaster. Everything worked great for a week, but then the new hard disk had the same problem that the old one had at first. WinXP doesn't boot. The installation CD doesn't detect any of the hard disks. Just the same, so it has to be a virus right? I can access the contents of the old hard disk booting from the MS-DOS disk. But I cannot access the contents of the new hard disk because its NTFS. Using very old Norton Utilities I can see the sector 0 of the old hard disk and there's something written on it: "Invalid boot sector". The new hard disk probably has the same problem. Questions 1) How can I repair a FAT32 HD boot sector? I wouldn't mind to format it and lost what I have there. That's already backed up. But my MS-DOS disk has no tools at all. 2) How can I repair a NTFS HD boot sector? I would like to access, if possible, a couple of files I didn't have the chance to back up. I got an evaluation avast! BART (Bootable Antivirus and Recovery Tools) but doesn't detect the NTFS HD nor the FAT32 HD and the system stop responding, just like with the Windows XP installation CD. 3) After doing that, I'm sure I'll be able to install WinXP again. What's the best antivirus? Norton is not. McAfee? Avast? PC-Cillin?