See Topic: What are Virtual Directories?
Adding Virtual Directories Manually
To add a virtual directory to your project, you can use :
Menu -> Virtual Files -> Add Virtual Directory
You will see a dialog box similar to the one below.

Local Directory Path - This indicates the path to a directory on your hard drive. The local directory is consulted during build time to obtain:
- Last modified date
- Creation date
- Last accessed date
- Directory attributes
Virtual Directory Path - This indicates where the directory will appear to exist when the application is running. Depending on the read-order selected, the directories properties may come from the hard drive rather than the virtual directory when both exist at the same place.
Add Files in directory - If this box is checked, Thinstall will also add files contained in the path pointed to by "Local Directory Path"
Add subdirectories - If this box is checked, Thinstall will add any subdirectories found in "Local Directory Path". This option is recursive, so the entire tree is added for any subdirectory found.
Special Note: Virtual files may exist at a path without the need for a virtual directory.