how to repair master boot record (MBR) in xp

a problem with the master boot record in a system may prevent the system from booting.MBR can be corrupted in several ways, it can corrupted by malicious code, by disk errors, or be overwritten by other boot loaders.but you can easily repair MBR using recovery console.go to the recovery console by either following ways from windows xp installation disk or Windows XP Recovery Console at startup (first have to install) for this example we get start from windows installation cd,

• Start your pc in with CD-ROM support and windows installation cd on it.
• When prompted, press R to repair a Windows XP installation.
• If you repairing multiple operating systems, select the appropriate one (XP) from the menu. If you have only one operating system, enter 1 to select it.
• Enter the administrator password if prompted
• To fix the MBR, use the following command
• fixmbr
• Type y and ENTER to fix the MBR
• Type exit and press enter to leave the recovery console and reboot system.

for additional info
to install recovery console in windows xp read this post