Safe Mode
Safe Mode is a troubleshooting tool for Windows. It works much like the command-line switches for Windows 3.x. Safe Mode that allow access into Windows using only the most basic drivers. 

• The AUTOEXEC.BAT and CONFIG.SYS files are not loaded. 
• The main portion of the Registry is not loaded. 
• In WIN.INI, the load= and run= lines are not loaded. 
• In SYSTEM.INI, the [Boot] and [386Enh] sections are not loaded.

Starting Windows 95 in Safe Mode bypasses the current real-mode configuration and loads a minimal protected-mode configuration. This disables Windows 95 device drivers and uses the standard VGA display adapter. If the problem does not occur in Safe Mode, it may be a conflict with hardware settings, real-mode configuration issues, incompatibilities with legacy Windows programs or drivers, or registry damage.

While Windows is in Safe Mode, the Device Manager should be checked for any hardware device conflicts. If there are conflicts, it may be necessary to change IRQ or DMA settings. If no conflicts exist, the problem is probably software related.

Safe Mode is the best troubleshooting tool Windows has, but Safe Mode does not state exactly where the problem is. There are several common things to do in Safe Mode.

• Turn hardware acceleration (Control Panel > System > Performance > Graphics) down to none.
• Turn read-ahead (Control Panel / System / Performance / File System) down to none.
• Change the video driver to a standard VGA (Control Panel > Display > Settings > Change Display Type). 
• Remember to restart the computer, booting to normal mode, each time something is changed.

If it is determined that the problem is software related, consider editing the WIN.INI file. Only two lines in the WIN.INI file do not load in Safe Mode. These are the run= and the load= lines. Remark out these lines by putting a semi-colon in front of them, then start the computer normally. If this solves the problem, then something being loaded on these lines is causing the problem.

If it is determined that the problem is hardware related, consider editing the SYSTEM.INI file. The [Boot] and [386Enh] sections in the SYSTEM.INI file should be examined. These are the only two sections that are not loaded when booting into Safe Mode. In general, any line that has an .exe extension is a program that is loading. Remark these lines out by putting a semi-colon in front of them. Also look for lines that access files with a .386 in them. These are old "legacy" drivers. These may be needed to run things like sound cards, modems, and so on, but most manufacturers now have updated drivers.

Failure to Start GUI
Sometimes the operating system files that control the Graphical User Interface (GUI) can become corrupted and generate an error stating a "failure to start the GUI". If this happens, choose to start the operating system from the DOS prompt or command line. From the DOS prompt, troubleshoot the operating system to repair the files that start the GUI.

DOS Modes
Depending on the configuration of the system, starting the system in DOS mode to troubleshoot issues with the system is also possible. Enter the DOS mode by selecting the Command Prompt Only option. Starting the system in this mode gives the ability to troubleshoot the operating system from the command-line interface. Command-line tools and DOS editors are available. Loading the HIMEM.SYS and the IFSHLP.SYS files or any of the Windows 9x files can also be avoided. Choose this startup option if the system fails to boot in Safe mode.

Win Switches
The Win switches provide the ability to startup Windows from the command line. The following are some examples of what can be done with these switches.

Use the WIN: /D switch to troubleshoot and isolate a number of problems with the operating system. Do this by modifying the /D switch to start Windows in a number of different configurations, then using these different configurations to start Windows with different options to troubleshoot specific areas of the operating system when it is not starting up properly.

• Use the /D:F switch to disable 32-bit disk access.
• Start Windows in Safe Mode or Safe mode with Networking by using the /D:M switch.
• Prohibit Windows from using the address space between F000h and FFFFFh by using the /D:S switch.
• Prevent Windows from controlling disk transfers by using the /D:V switch; instead, the hard drive disk transfers are handled by the BIOS.

The various types of switches allow users to manipulate the Windows operating system in a variety of ways to troubleshoot specific areas of the operating system.