Guide: Repairing Windows XP Master Boot Record
What exactly is the Master Boot Record?
A small program that is executed when a computer boots up. Typically, the MBR resides on the first sector of the hard disk. The program begins the boot process by looking up the partition table to determine which partition to use for booting. It then transfers program control to the boot sector of that partition, which continues the boot process. In DOS and Windows systems, you can create the MBR with the FDISK /MBR command. (Thanks to Webopedia)
How does the MBR most commonly become damaged?
Lately it seems more people have begun to use Linux, or dual booting in general. When you install a second operating system like Linux, the records of the O/S must be written to the MBR to make the option open to boot to that O/S. It seems that it is very common people just delete the partition of Linux (when they want to uninstall), and go to reboot. Because the MBR is looking for a partition that no longer exists, it crashes and no operating system is loaded.
How will I know when my MBR is crashed?
I haven't seen many MBR viruses around lately, so I'd say you'll know that you probally caused something with an experience similiar to above. With a corrupted MBR like that, the system will just get to the point of normally loading an O/S and then restart.
How do I repair my MBR?
The easiest way to repair your MBR records is with a Windows XP disk. Simply put the disk in, and allow the computer to boot up from the disk (you may need to set it to boot off of CDs in BIOS) and it'll come to a main menu.
Click R for Repair Console.
In the repair console, type 'fixmbr' and press Enter.
It will prompt you for an Administrator password, and you can almost always press Enter with nothing in there.
Your MBR has now been fixed, and Windows XP will now load back up.