I'm hoping my experience here will help others. The other night, I installed a new multi-function printer, and removed the previous printer, followed by a reboot and checked it worked. I downloaded a free add-on picture software for the printer scan function, and tried it. I saw my antivirus update, received MS patch-Tuesday notification and gave permission for the download but not installation of that. Last I uninstalled the previous scanner software, then closed down for dinner. Reboot was normal until the 'welcome' screen should appear, when instead there was a pop-up 'Isass.exe - system error'. 'Object name not found. Ok'. I press ok and the PC reboots - in an endless cyle. Now I am pretty experienced in this sort of thing, so I followed procedures Reboot into safe mode - no change Reboot into 'last known good' - no change Reboot into command prompt and run chkdsk /f - two errors corrected but no change I could not very easily roll back to an earlier restore point with no working Windows to do it from (you can do it from Recovery Console on an install CD, but I have no install CD - there is only a 'recovery partition' on my OEM PC) I could easily borrow an install CD in a day or so but I know how to do a restore-point recovery without one anyway, using a Linux boot CD and physical copies from very weird places under system volume information, so I restored to the previous day and still no joy. By now I was still not certain if the problem was installed software or a virus, but hardware was less likely because under Linux everything checked out fine. My activity previous to the fault made a virus less likely than a software fault, and suspicion fell on the last thing I remembered doing - uninstall of scanner software. It looked to me as if the registry still called for some software removed by the uninstall - a driver in other words - and uninstall routines are notorious for leaving things behind capable of tripping Windows up. So out comes the ultimate weapon - restore from image. Forty minutes later I was running again. Yet another example of the vital importance of imaging your PC. Please be aware that the design of Windows is poor enough not to be able to cope with a missing driver amongst many, many, many other relatively simple problems. To the credit of Dell for one, an imaging solution of sorts is bundled with their PC's - even if only a time-limited trial. Of course, imaging is not quite perfect, because images always tend to be a little out of date (they take too long to be used daily), so as in my case there is usually a bit of recovery from daily backups to do, and maybe installs or configuration changes as well. And do be aware, your PC setup should always have separate partitions for installed OS plus programs, and data. That way, lose your OS you still won't lose your data, AND your image will not be enormous. Your OS and program installs is what needs imaging, your data needs frequent backup. Thank you for reading.