Windows registry hack improves offline file access for mobile users

There may not always be enough free space to accommodate all the files you want to make available offline. Fortunately, you can use a simple registry hack to designate another volume to use for offline caching.


When I was a network administrator, dealing with mobile users often made me want to rip my hair out. It always seemed as though my mobile users were asking for the world and that I could never make them happy. After all, sometimes it just isn't practical to give end users access to everything they want when no connectivity is available.

Still, as someone who travels frequently, I do understand why mobile users want access to the entire network, even when they are offline. As an administrator, though, I'm also keenly aware of the technical hurdles involved in doing so. Fortunately, most of my trips have been relatively short, so I've been able to copy the files I need to my laptop, and then copy the revised versions back to my network when I've returned.

Unfortunately, this changed last fall, when due to a personal emergency, I was forced to be out of state for about two months. Since I didn't have a lot of time to plan for this trip (it was an emergency after all), I bought a laptop with two hard drives and copied as much data as I possibly could to the second hard drive.

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My plan was to work off of the copy of my data while I was away, and then copy the files back to my network when the trip was over. Although it was a good plan, it was flawed because at the end of my travels I had to figure out which copy of each file was the current version, and then merge the data from my laptop with the data on my network. Luckily, I had created an excel spreadsheet in which I made a log of all of the files I had modified while away; but merging the changed files was still time consuming and tedious.

As you probably know, every version of Windows since Windows 95 has had an offline files feature (although the feature's name has changed from one version of Windows to the next). Therefore, you might be wondering why I chose to do things the way I did rather than just use Windows Vista's offline files feature.

The reason is because Vista's offline files feature (officially known as Client-Side Caching) isn't very flexible. Let's take a look. To access the feature's properties sheet, do the following:


  • Open the Control Panel and click on the Network and Internet link

  • Select Offline Files

  • Select Manage Disk Space Used by Your Offline Files

Figure A

As you can see in Figure A, Windows Vista allows you to limit the maximum amount of space that offline files can consume, but it doesn't allow you to control where those files are stored. In case you are wondering, Vista stores offline content in the C:\Windows\CSC folder.

The reason I didn't use the Client-Side Caching feature during my travels was that my C: volume simply did not have enough free space. Between all of my applications and several different virtual server instances, there just wasn't enough room left over for data. That's why I bought a laptop with a second hard drive.

When my trip was over, I realized that I really needed to find a better way of managing my files when I am on the go.

Fortunately, I found a way to redirect offline content to a different location. However, doing so involves editing the registry, which, as you know, can be very dangerous since making a mistake could destroy Windows. Therefore, I recommend making a full system backup before you attempt the procedure that I am about to show you.

For the purposes of this article, I am going to assume that the laptop does not currently contain any cached offline content. With that said, open the Control Panel, and click on the Network and Internet link, followed by the Offline Files link. When you do, Windows will display the Offline Files properties sheet, shown in Figure B.

Figure B

Notice in the figure that the properties sheet's General tab tells you whether offline files are currently enabled or disabled. Disable offline files if they are currently enabled, click OK and reboot the machine.

When the computer reboots, open the Registry Editor and navigate through the registry tree to HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\CSC. Next, create a new string value named Parameters. The value that you assign to the Parameters key is going to vary depending on the path that you intend to use for storing offline files. In my case, I am storing my offline files in a folder named E:\CSC, so the value that I entered was: \??\e:\csc. This is a literal value, and the question marks should be typed as they are shown in the previous sentence, not replaced with something else. It's also important that you do not manually create the destination directory ahead of time.

When you are finished, exit the Registry Editor and reboot the computer. When the machine reboots, go ahead and enable offline files. While you are on the Offline Files properties sheet, go to the Disk Usage tab and make any necessary adjustments to the amount of disk space that can be allocated to offline files. You can also use the properties sheet's Encryption tab to encrypt cached content if you so desire.

Once you finish making any necessary adjustments, reboot the computer one last time. When the machine reboots, you can start making folders available offline.

Brien M. Posey, MCSE, has received Microsoft's Most Valuable Professional Award four times for his work with Windows Server, IIS and Exchange Server. He has served as CIO for a nationwide chain of hospitals and healthcare facilities, and was once a network administrator for Fort Knox. You can visit his personal website at

This was first published in July 2008

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