disabling the f8 key for bootup

Find the file msdos.sys which can be find at c\msdos.sys. Since this is a hidden system file, you will have to make it writeable by changing it’s attributes by going to the DOS Prompt and typing the following
go to the root directory

C\Windows>cd\

Then make msdos.sys writeable and unhide it by typing

C\>attrib msdos.sys –h –w

3)Open msdos.sys in WordPad

4) You will see something that looks like this

;FORMAT
[Paths]
WinDir=C\WINDOWS
WinBootDir=C\WINDOWS
HostWinBootDrv=C
[Options]
BootMenu=0 (default)
BootMulti=1
BootGUI=1
DoubleBuffer=1
AutoScan=1
WinVer=4.10.1998
;
;The following lines are required for compatibility with other programs.
;Do not remove them (MSDOS.SYS needs to be >1024 bytes).
;xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxa

To disable the function keys during bootup, directly below [Options] you insert the following piece of code

"BootKeys=0."

(Without the quotes of course.)
Now instead of inserting the BootKeys command you can also insert the following command

"BootDelay=0."

Not many people know about the BootDelay=0 command so that along with the BootKeys command does make your machine safer. Then save msdos.sys.

5) Since msdos.sys is an important system file you should change it’s attributes back to read only and hidden by typing

c>attrib msdos.sys +h +r

it is from ankit fadia's book