windows 2003 server: repair affects any software or data

everything was ok in a sunny friday when I realize that one of the w2k3 servers just crashed; it didn’t have a bad aspect, I thought, just reboot it and that’s it; it didn’t work.

The error on the screen:
“LSASS.EXE – System Error, security accounts manager initialization failed because of the following error: Directory Services cannot start. Error status 0xc00002e1.
Please click OK to shutdown this system and reboot into directory services restore mode, check the event log for more detailed information.”

I tried to find out a quick solution, but the one I consider the best is to reinstall the OS.

My question is, reinstalling the OS affects any other software or data or just goes against the system files/folders?

thanks in advance!