Windows Vista relies on the Windows Boot Manager to locate the information the computer needs to boot to the operating system. If the Windows Boot Manager, called BOOTMGR or bootmgr.exe, is corrupted or missing, however, the TOSHIBA Satellite L355-S7905 will not be able to load the OS at startup.
When the computer turns on, a critical software, called the basic input/output system, checks the installed devices for problems, loads the hardware and runs the instructional code found in a sector of the hard drive called the master boot record. The MBR, also referred to as the boot sector, initializes the Windows Boot Manager, enabling the computer to locate and run the boot configuration data found in the active partition -- a segment of the hard drive where Windows Vista is stored. If the computer can't find BOOTMGR, the Satellite L355 won't find the active partition or the BCD.
Boot sector viruses are made to invade the MBR, altering the machine code found in the sector so that the computer can't load the OS or find the necessary data to run the boot files. These viruses also alter the code so that the infection can be spread to other bootable devices, although this isn't a problem with laptops unless the installed disk drive is connected to another computer temporarily. Run an antivirus application from CD, DVD or USB to check for and remove malicious software.
Hard Drive Failure
If the hard drive is damaged, the TOSHIBA Satellite L355-S7905 will fail to read data on the corrupted portions of the drive. If the segments of the hard drive that hold the MBR or BOOTMGR are corrupted, the L355 won't be able to access that information. These damaged segments, called bad sectors, can be "removed" -- hidden so the computer won't attempt to read or write to them in the future -- but if the damage is bad enough that the Satellite can't read boot data, the drive should be replaced.
If the MBR or BCD are corrupted due to malware or user error, the computer might fail to find BOOTMGR, even if it's still on the hard drive. Startup Repair, a software utility installed to the Windows Vista DVD, can recover the boot data automatically. The TOSHIBA Satellite L355, however, doesn't come with the Vista DVD, but is, rather, packaged with a recovery disc that reinstalls the entire OS. If you have a copy of a 32-bit Windows Vista DVD, you can run Startup Repair from the disc to repair the OS. Otherwise, you must reinstall the OS to the S7905.
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