[newbie] no more X server

[Frederic Rooms]

Hello,   I was working on linux mandrake 8.0 with scilab,netscape. I was not installing a rpm or something else: just working as a normal user. Suddendly, I tried to increase the stacksize of scilab when it crashed. I was surprised but continued to work. I tried to print: no more lpd server availabe. I logged out and restarted the pc: no more x server. It stops at the screen asking for a username and password and the return to level 3 ! I tried to upgrade the system with the original cd because I thougt I could reinstall the X server. When I boot on installation CD, it works until it checks for the installation package and says: "segmentation fault: missing memory. Install crashes". Has anyone a solution ?   thank you   Fred