You can find your boot.ini file in the root directory of the drive in which your operating system is installed, for example if you have you OS installed on C drive then you will find the boot.ini file in c:\boot.ini

Make sure that you have show hidden files turned on in you folder options.
Make a backup of the current boot.ini file

[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional" /noexecute=optin /fastdetect

Note: This is how my boot.ini file looks like, Your boot.ini may vary from this.

Now how to do the Tweaking:

Edit the original boot.ini with any text editor like notepad or word pad so it appears as shown below.

[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional" /noexecute=optin /fastdetect
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional Safe" /fastdetect

Note: The second line shown above is the line you have to add. I used the word “Safe” but this can be any word you choose.

Close Notepad and save changes when prompted.

Start the System Configuration Utility by clicking [Start] [Run] and typing msconfig, then click [OK].

Click the BOOT.INI tab.

Highlight the boot line that you added with the word “Safe” or whatever word you chose to add above.

Check the /SAFEBOOT option in the Boot Options box and click on the radio buttons to add whatever options you prefer. I’d suggest the MINIMAL option.

When you check the /SAFEBOOT option in the Boot Options box it will add /safeboot:minimal to your highlighted boot line

Your final boot.ini would look like this:

[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition (1)\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Micro soft Windows XP Professional" /fastdetect
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional Safe" /fastdetect /safeboot:minimal

Click [Apply] and [OK] and Restart when prompted.

The option to boot into safe mode will now appear as “Microsoft Windows XP Professional Safe” on the boot loader menu select this item from the boot menu to boot with Safe Mode.

Note: If by any chance you mixed up with the code just replace the boot.ini file you made backup of with the modified one.

Related: Make Windows Xp Remember Last Open Folders on Next Login