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Windows XP Boot Sequence

How a Computer Starts Its Day

Oct 7, 2006 Michael Simpson

Ever wonder what happens from the time you turn your computer on until you see the

Windows login screen !et me tell you a"out it#

When you hit the power "utton on your computer a whole lot of stuff happens# We call

this the "oot process# $n the days when $ first started using computers there was literally a

%"oot dis&%, a floppy '(#2(% not a )#(%* dis& that told the system where to go and what to

do so that the operating system would start up# Since then the "oot se+uence has "ecomesomewhat more complicated# So let me ta&e you thru the steps the computer ta&es to get

started# or my e-ample $.m going to use a Windows / system#

irst is the OS1, this stands for ower On Self 1est, for the computer# 1his

process tests memory as well as a num"er of other su"systems# ou can usually

monitor this as it runs each test# 3fter that is complete the system will run OS1

for any device that has a 4$OS '4asic $nput5Output System*# 3n 3 has its own4$OS, as do some networ& cards and various other devices#

Once the OS1 is complete and the 4$OS is sure that everything is wor&ing

properly, the 4$OS will then attempt to read the M4 'Master 4oot ecord*# 1hisis the first sector of the first hard drive 'called the Master or 890*# When the

M4 ta&es over it means that Windows is now in control#

1he M4 loo&s at the 4OO1 SE:1O 'the first sector of the active partition*#

1hat is where ;1!9 is located, ;1!9 is the 4OO1 !O39E for Windows

/# ;1!9 will allow memory addressing, initiate the file system, read the

"oot#ini and load the "oot menu# ;1!9 has to "e in the root of the active

partition as do ;19E1E:1#:OM, 4OO1#$;$, 4OO1SE:1#9OS 'for multi5OS"ooting* and ;14OO199#SS 'if you have S:S$ adapters*

Once / is selected from the 4oot Menu, ;1!9 will run ;19E1E:1#:OM,

4OO1#$;$ and 4OO1SE:1#9OS to get the proper OS selected and loaded# 1hesystem starts in

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