I have a Dell Optiplex 745 running Windows 7. I left town for 4.5 days and when I came back it refused to start. I mean that it would show the dell screen but with blue lines running down it and then go to the windows loading screen w/ the balls of light. After that it just goes to a black screen and stays there, no mouse pointer, etc. If I use start-up repair, it runs then asks if I want to use system restore. Tried it, didn't work. After that it ends up saying "Start-up Repair cannot repair this computer automatically. Problem Signature: Problem event name: StartupRepairOffline Problem signature 1: 6.1.7600.16385 Problem signature 2: 6.1.7600.16385 Problem signature 3: unknown Problem signature 4: 62 Problem signature 5: AutoFailure Problem signature 6: 1 Problem signature 7: NoRootCause OS Version: 6.1.7600.2.0.0.256.1 Locale ID: 1033 " At the end of the diagnosis and repair details, it says "repair action: System restore result: canceled repair action: System files integrity check and repair result: failed Error code=0x490 time taken=624020 ms" The computer starts in safe mode and the memtest runs clean. Do you have any suggestions on how I can fix this?