Help!! I am new to this site and I have found a lot of useful information. My computer is running very slow. I get a message when I log on that the sfc_os.dll file was not found, but I went to the System32 file and there it was. I thought it may be corrupted so I tried replacing with the file from the ServicePackFiles but I get a cyclic redunancy check error message.

Hello thalia0266

and welcome at Gladiator Security forums. We are glad you joind our small little community.
The problem you told us is an old but known one:

http://gladiator-antivirus.com/forum/index...showtopic=26927

Have a great day

B. Udo

Thanks but I tried doing this yesterday. My System32 folder already contains the sfc_os file. After reading this post I figured it must have been corrupted, but when I tried replacing it wth a file from ServicePackFiles I got an error message: "cannot copy: cyclic redunancy check"

Hi thalia

that error message might be another, additional problem causing it.
Please make sure you're following the advices given in that link before. This is very important!!!
To make it easier for you, here the main parts in compressed mode:

1. Because XP will not always show you hidden files and folders by default. Reset your search settings first:

* Open Folder Options>view and check your settings:
* Select --> Show hidden files and folders
* Display the contents of system folders
* Uncheck: Hide protected operating system files

Next go to Search and look down to More advanced options and click onthe chevron next to it.

Be sure the first three boxes are selected:
** Search System folders
** Search Hidden Files and folders
Search SubFolders
--------

Have a look in your C:\windows\system32 folder for this file: sfc_os.dll

If there, it may be corrupted. If not there, we need to replace it with a good copy either way. Do you have your service pack files on the hard drive? (you must use the sfc_os.dd file which corresponds to your system, means if you're running SP1, the file must be from SP1 etc.

Let's try this.

* Search for this folder i386
* Then look for sfc_os.dll or sfc_os.dl_

Same file, but one format is compressed and the other isn't.

The idea is to put a good copy of the ifle into the system32 folder. IF it is compressed, we'll need to expand it. That's not a problem.

You want this one:
C:\Windows\ServicePackFiles\i386\sfc_os.dll

Right click on sfc_os.dll
Click copy from the menu

Open C:\windows\system32

Right click on an empty space in that folder and click Paste on the menu.

Now you should have a good copy of sfc_os.dll in the system32 folder.

If you have system32\dllcche folder, put a copy in there too.

Try a restart and see if the error is gone, or if you get another one due to some other missing file.

Greetz
BU