@Richard: thanks for the helpful assistance in my absence. Please continue to offer anything you believe might help as it seems that we are approaching the drastic step of a clean installation and though I'd like to avoid that, I'm not seeing very many alternatives at this stage.
@jerm1,
It always works from the Neosmart Recovery disk if you cd to D:\Windows\System32 (I'm saying D: because that's apparently where Vista is on this machine - ???) and then run it. That plus running it with that disk makes it run in elevated mode. I've done it and had it done hundreds of times before and never had this problem (except where I couldn't access the hard drive at all). I cannot understand why it is not working in this case.
I think the problem is that we somehow still aren't in D:\ though I can't understand how that can be and yet you can get to those folders and that command (and a dir command lists all sorts of files and directories - much more than would be on the disk so I don't think it's a dir of the disk). I'm also beginning to think that the hard drive may have failed to the point that it isn't functioning even with basic commands (though it seems to respond to dir - though that may be coming from the disk, but sfc may be too much for it).
Please try again to get to D:\Windows\System32\> to run the command. Remember, no space after the > and the command is sfc /scannow and then you enter. If you get the same error message, type chkdsk /f /r and then enter and see what happens. If it asks you to run on the next restart answer yes and then remove the cd and reboot.
If that doesn't work, then perhaps we need to go with Richard's suggestion to save the data using Ubuntu (or slaving the drive to another computer) and then try a repair installation or a clean installation or a restore to factory conditions. I'm still not clear on what you are planning to use to restore the system - you can't do a repair install, clean install or a restore to factory conditions with the Neosmart Recovery Disk. You need an installation disk that contains the operating system. To do a repair install, you need a genuine Vista installation disk and you need to be able to boot to the system (and since you can't boot to the system, I think that leaves us with a clean install). Can you please tell me how you would do that if it is required?
Thanks and good luck!