Replacing Active Files

Just a few weeks ago, during the IE4 "New Window" bug fiasco, I was asked to do all this reinstalling and so forth basically in order to replace one DLL with an older version (just to see if file corruption was the problem, no less).

However, the topic's come up before. Like when a new driver comes out, but the install program has failed for some reason, and you just know all you have to do is get this one file in the right place for everything to work.

Sometimes, you can simply select the old file, rename it, then copy the new file into its place. It's worked before, and is always worth a shot, but more than likely you'll get an error message about the file being in use.

There are a few ways you can go about this file replacing business (not including having another operating system): using the method the installation programs themselves use (the Registry method); using the Resource Kit's mv.exe POSIX utility; and Microsoft's somewhat more convoluted method involving the Emergency Repair Disk.

Of course, since the files involved will probably have the same name, you'll usually want to rename the new file, maybe just by changing its extension to "new". Then you can place it in the same directory as the file to be replaced.

Replacing Active Files --
Using the Registry

The easiest way to replace an active file involves using the Registry, the way installation programs do it: adding two entries to the following Registry key for each rename operation:

HKLM \SYSTEM \CurrentControlSet \Control \Session Manager \PendingFileRenameOperations

On the next boot, the system checks this key, and if it finds anything there, performs the operations.

The two lines you need to add are the source (the new file) and the destination (the file to be replaced), and you add them by

1. selecting "Add Value" from the Edit menu
   
2. leaving the Value Name blank
   
3. selecting the REG_MULTI_SZ data type, and
   
4. entering the file paths into the Multi-String editor in the following formats:

   \??\{full NEW file path} !\??\{full OLD file path}

   Example:

   \??\C:\WINNT\NEWFILE.NEW !\??\C:\WINNT\OLDFILE.DLL

Replacing Active Files --
Automating the Registry Method with mv.exe

mv.exe is a POSIX port to NT that lets you schedule file move operations for the next reboot. mv.exe is included with the NT Resource Kit, and you have to have the Batch Utilities from the RK installed from the CD. (See the RK link above about how to install just one RK program, instead of all RK programs, by using the RK Help Files to determine each utility's necessary files).

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