okay... so i tried to run my pc and i get this whenevr it starts right after the motherboard logo...
"windows couldnot start because the following file is missing or corrupt :
WINDOWS\SYSTEM32\CONFIG\SYSTEM

you can attempt to repair this file by starting windows setup using the original setup CD-ROM
select r at the first screen to start repair"

so i tried to enter my xp cd but it does not start at all cause just after motherboard logo i get the same error message and if i clicked any button the pc restart itself...
it once ran by luck i pressed r and it asked me this :
which of the folowing installtion would u like to log on?
(to cancel, press enter)?\ "
i was suposed to write something but i dont know ... but lets first solve how to run the cd then solve the repair ...

note : i am running my xp cd in a dvd rom if that matter for anything..
note 2 : no i dont have a cd rom its broke...
note 3 : its proably corrupt not missing cause i was getting a message by some corrupt files in windows lately...
note 4 : this my laptop..
note 5 : thanks for support

First, make sure the boot order in BIOS lists CD drive as the first booting device.
Then, put CD in, restart computer.
At some point, you should see this:
Press any key to boot from CD
Press "any" key, and...
....follow the steps from here: Icrontic Repairing Windows XP in Eight Commands

okay this looks like it might work but i am facing a problem..
the boot from cd thingy worked fine..
now at the repair thingy .. on the second page of the post u mentioned b4 he said..
To “Go up a directory” in computing is to revert back to the directory above the current folder you’re operating in. If, for example, I’m in the C:WINDOWSSYSTEM32 directory, and I want to get at a file in the WINDOWS directory, I would merely type CD .. and I would be taken out of the SYSTEM32 folder and up one level to WINDOWS. We’re going to do the same thing here from the WINDOWS folder to get to the basic root of C:

i dont get that .. what should i type?
note:
i am in C:\WINDOWS
and i tried to type cd but it did not work can u explain it to me??

Type cd.. again (don't forget about two periods after "cd").

thanks that worked i am completing the rest of the commands now stay tuned

Bring us good news

okay now another tiny problem..
he says :Secondly, if you are the owner of a CPU featuring Intel’s XD or AMD’s NX buffer overflow protection, you must also use /NOEXECUTE=OPTIN as an OS Load Option. I will demonstrate both commands for the purpose of this guide, but do not set NOEXECUTE as a load option if you do not own one of these CPUs

how do i know if i am one of the owner of these cpu's?? note : i know nothing about cpu's
by that i mean i dont know its kinds and models and versions... silly me

Most processors have NX buffer overflow protection, so you safely assume, yours has it too.

lol.... that for some reason did not work..
i made all the steps right except for chkdsk one which he said is not important but i get the exact same error message whenever i try to run it.. should i try again but with out the cpu thingy>??
here is a note : i do own 2 xp pro cd's both of them used for the same computer...
since my windows crashed alot i bought a new copy and installed it on pc anyways it crashed again so i just kept installin this for some time then the other one for another time and so on...
but here is a question .. does the same windows cd must be used??
lets say i got the new one installed and i used the old one... make any differnce??

No, all CD are equal.
Try Windows repair: How-to repair Windows XP