The Windows XP DLLCACHE Folder

The folder in which Windows XP stores protected system files is called dllcache and is stored in the WINDOWS\system32 directory. Because of the importance of this folder, it is marked with both the System and Hidden attributes, making it completely hidden in the Windows Explorer interface by default. If you want to be able to view the folder through the Explorer interface, open My Computer, access Tools > Folder Options, click the View tab and then select the Show hidden files and folders option, and uncheck the Hide protected operating system files option. Keeping hidden system files hidden is highly recommended, so consider opening this folder from the Run command instead – in the Open text box, type %systemroot%\system32\dllcache and press OK.

Although there is no maximum size for the dllcache folder by default, the amount of available disk space will impact how many files it is capable of caching. If a maximum size in MB hasn’t been specified with the sfc /cachesize command, the dllcache folder will can consume disk space up until the point that only 600 MB plus the maximum size of your paging file is available – after this, no additional files will be cached. On bigger volumes this won’t be an issue, but on smaller disks the number of files that can be stored in the folder will be minimal. Thus, if WFP needs to replace files, you’ll be prompted for your CD often, which can quickly get annoying. If you have lots of available disk space, moving the dllcache folder to a new location (such as a different partition) makes it possible to cache all system files, and avoid these annoying CD prompts.

The only way to change the location of the dllcache folder is via the Registry. To do so, open Regedit.exe and create a new value of type REG_EXPAND_SZ in the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon folder called SFCDllCacheDir that specifies the path to your preferred caching location, for example d:\systemfilecache.

Author: Dan DiNicolo

Dan DiNicolo is a freelance author, consultant, trainer, and the managing editor of He is the author of the CCNA Study Guide found on this site, as well as many books including the PC Magazine titles Windows XP Security Solutions and Windows Vista Security Solutions. Click here to contact Dan.