BleepingComputer.com: Sfc /scannow

On : sfc /scannow, what and when and how do you use this application? Thank you very much. YOYO.

The System File Checker will compare the file versions of "protected system files" on your system with your original installation media - and will replace those that don't agree with the version on the installation media.

This then requires a visit to Windows Update to ensure that you haven't "down-dated" any of the protected system files that were updated by Windows Update.

Also, it's not a friendly tool - it won't tell you when it's done and won't suggest anything but to insert your XP CD.

It's the step that I take just before recommending a repair install of XP. I haven't found a list of the "protected system files" but suppose that it's easy enough to locate.

Remember that the "protected system files" are only a sub-set of "system files" - so that it won't fix all problems. Also, if these files were "protected" in the first place - how did they get changed? (just food for thought).

Here's a HowTo about it: http://www.bleepingcomputer.com/forums/topic43051.html

USASMA SIR: I will check out the site you have facilitated. Can you tell me under what condition(s), would I use this tool? If I have been advised to do a repair or reinstall of XP, should I try this first prior to embarking on repair /reinstall XP? Do you use this tool?/when & why did you this tool? I had an issue with installshield scripting engine missing, in which I was advised to to do a reinstall/repair XP, would using sfc/scannow being suffice in bringing about resolution to enable me to reinstall ITune?? Since this tool is applied to check protected system files, and been protected files in the first place, if some files were changed- how were they altered or been manipulated??? I am really scratching my head on this one, please enlighten me !!!! Thank you very much for all your assistance. you really make the difference. And I learn so much from you each day. APPRECIATED. take care. YOYO.

Using this tool is appropriate if you think that there may be problems with "protected system files". It definitely can't hurt to use it before going through with a repair installation of XP - but don't expect it to be cure-all for problems like this (I expect to be of more use with errors in the operating system itself, rather than with external stuff like install shield, etc)

"Do you use this tool" No. But not because of it's abilities - but rather I find it easier to restore my system with an imaged copy that I keep rather than troubleshooting the constant problems that I face. I highly recommend it's use when appropriate.

Here's some links about it from Microsoft:
http://support.microsoft.com/kb/222193/EN-US/
http://support.microsoft.com/kb/222473/
http://msdn.microsoft.com/library/default...._start_page.asp
http://msdn.microsoft.com/library/default...._windows_xp.asp

Also, there's this great freeware tool that I also advise using in certain circumstances (such as installshield not working): http://wiki.djlizard.net/Dial-a-fix#Standard_version

USASMA Sir: Sfc/scannow appeares to be a practical utility, unfortunately it is not a cure all as I was hoping that it can replace repair installation of XP. Now, since this utility specifically deals with protected system files, If I experienced a system error, would the given situation warrant the usage of sfc/scannow as a viable solution? Sure will check out those sites that you have suggested at MS. The link for the software you had provided, appears to be a tool that I can really use when related issue arises again with Installshield. Tell me, this software, would it be useful when I receive this message:" ---Installshield Script Engine is missing--run ISScript.msi.....?? One more thing, you did not tell me those "protected system files", if any are changed, being they are "protected", how were they changed???? I implore you to Please tell me, I cannot figure this one out, and I am dying to know! THANK YOU VERY MUCH SIR for all that you do. You really make the difference. Regards. YOYO.

Hi YOYO!

Well, now you're getting pretty deeply involved in stuff that I don't fully understand myself.

The DJLizard program is a good tool when a program won't work because of an unregistered dll. This can happen many different ways, but none of them are very obvious. I use it as a "just in case" tool when there's a problem with one of the specific programs listed in DialAFix.

Protected system files can (I think) differ from system to system. They're also stored (at least some of them) in the dllcache folder on your system, but I suspect that there's another location that stores information on them also.

They were changed because something got around the protection. The protection isn't a total block from changing them (otherwise you'd never be able to update them) - but it's rather that they're more protected than other system files.

Viruses can do this, Windows Update can do this, even random data corruption can do this.