Well ya,here is the problem
Windows could not start because the following files is missing or corrupt
\WINDOWS\SYSTEM32\CONFIG\SYSTEM
my brand is samsung
ok, so, this time, a screen with saying insert a xp cd and press "r" to repair it had appear after the boot. here's the problem. This laptop is originally vista, so it came with only vista software disc. But then i changed it to xp by installin xp in it, and i did it in some other country few months ago, so i don't have a xp cd. Now here's the real problem

The screen with the "r" for repair should be after the boot, but after i press something like f4 or f7 for using backup, restore and install function during bootup, then the screen for "r" repair has disappear, now everytime i start the laptop up, only a screen with a flashing "_" appears. how can i fix this problem? and i don't want to reinstall window cause i have some important files in it.

hope someone can help me on that. thx

the second R is only there in full version of winxp ,not in recovery cd's or recovery images

You can always get your data off by attaching the HDD onto another PC. Then you can re-build your Windows.

That's provided it's only data you're worried about. Applications - well I hope you have the install stuff.