Every time Windows starts up, a number of programs are run automatically. Most of the application that you install using default installation like a virus scanner or an instant messenger application, also load when the Windows boots up. These applications use the system memory and take time to get going, leaving little portion of the memory for other programs to open. Some programs sneak into the list of programs that are loaded during start ups. This results into slow start ups if you do not have enough memory.

Windows start up issues can also be caused by a program that is deleted mistakenly, a program that failed to install or uninstall itself properly, or the wrong drivers of peripherals etc. While starting up, a number of reasons cause the Windows to freeze including:

• Malfunctioning hardware 
• Corrupt driver
• Corrupt file or volume
• System misconfiguration
• Any electronic infection including virus, Trojan horse, spywares etc.

Failure of some components of the hardware is one of the common reasons behind Windows start up problems. This hardware failure could range from unplugged power cord to some serious problems like smoke emitting from the system. updates of the drivers or the BIOS also cause start up woes. If some key operating system files has become corrupt or has gone missing, it will bring your system to an abrupt halt. Misconfiguration could also be a possible reason behind Windows failing to start. Though you may be able to start up your computer, some services or application may not function. Virus infections can also stop your computer from starting up.

Running the troubleshooting utility, MSConfig, enables you to see the programs that are loaded during startup and edit .INI files, services and startup files. You are required to have Administrator's rights to use this utility.
For running MSConfig utility:

• Click on Start and then Run
• Now type in MSConfig and enter
• Click on Start up

This will show you the list of programs loading during the start up. MSConfig utility functions as a basic startup manager but you should not utilize it to disable startup application or alter auto-start programs as doing that would mean:

• Changing the system registry which holds critical services that are a prerequisite for hardware and booting. If you uncheck a service, you will end up disabling it completely.
• If you tamper with a certain program with MSConfig, it may not uninstall properly and orphaned entries might be left on the registry.
• Orphaned entries can manifest themselves as boot up errors when you switch back to normal startup mode.
• MSConfig utility does not show all the applications loaded in all possible startup locations, a few entry points remain hidden from the user.
• Disabled entries cannot be removed completely from the list of programs displayed by MSConfig.

It is advisable to use a startup manager rather than the MSConfig as it allows you to experiment and see how your system performs with any of programs disabled. But before going for this you should create a restore point which you can fall back on in case of a critical issue.

• Go to ‘Start’ and click on ‘Help and Support’
• Select the ‘System Restore menu’
• Click on ‘Create a restore point’ and then ‘Next’
• Type in a name for the restore point and then click on ‘Create’
• Click on ‘Close’

Now the restore point has been created and you can fall back on this point if you face any issues while editing your startup.

• In order to enhance the performance and speed of your computer you can do the following.
• Remove all applications and programs that you do not use
• Delete browser's history, temp data and your Favorite or Bookmark list.
• Clean the Windows Registry
• Get rid of threats like viruses, malware etc by doing a proper scan
• Free your system memory regularly
• Schedule your cleanup programs to run automatically
• Defrag your disk and volumes and organize your files
• Optimize and tweak your computer regularly

Careful diagnosis holds the key to fix the start up problems effectively. You should look for following symptoms to ascertain start up problems.

• "NTLDR is missing"
• "Error loading operating system"
• "Windows could not start because the following file is missing or corrupt"
• "Invalid Partition Table"
• "Missing Operating System"
• "A disk read error occurred"
• System hangs after BIOS POST finishes
• "Windows could not start because of a computer disk hardware configuration problem"
• "Could not read from selected boot disk"
• "Check boot path and disk hardware"

The probable causes of these errors vary from corrupt master boot record, hard disk, virus infection, corrupt boot sector and corrupt or missing Boot.ini file to corrupt Boot volume.
Following are some of the primary tools that are used to resolve Microsoft Windows start up problems.

• Last known good. To restores certain parts of the registry.
• System Restore. To restore computer to a previously saved configuration.
• Safe mode. To starts Windows with a minimal set of drivers and create their records.
• Automated System Recovery (ASR). To restores the boot volume from backup
• Repair. To run Windows Setup from your product CD and to try and repair your installation.