I got a black screen after I started my computer. Thanks for your suggestions, which helped me resolved the above problems by following the steps below: 1) I cold booted my computer with the six windows xp startup disks, which I downloaded from Microsoft website 2) After it booted, I hit R. This is option two which allows Windows to repair. After I typed in the administrator logon password, it gave me a C:\windows\> prompt 3) I typed chkdsk /r. This took hours to run. Finally my patience paid off. I then typed exit and followed steps 1 and 2 again. 3) At the windows prompt, I typed expand d:\i386\comdlg32.dl_ c:\windows\system32 (Btw, d: is my CDROM drive where the Windows XP CD is placed) 4) After the file had been expanded, I then typed exit at the c:\windows\> prompt, which then restarted Windows XP. As a note, it seems that if either comdlg32.dll or ntoskrnl.exe is missing, one cannot start or access the XP logon window. One can follow the same procedure if the file ntoskrnl.exe is missing. In this situation, type expand d:\i386\ntoskrnl.ex_ c:\windows\system32 If anyone knows what caused these files to be removed from the system please let us know.