One or more paths on your network is not set to write access.
Run Store Operations Administrator and select File, Configuration, Paths tab. You need read/write access to all paths listed. The same goes for the Templates tab if you have set any templates to a network path.
Normally all entries on the Register, Paths, and Templates tabs should be set to the local C: drive except Pictures, Labels, Reports, and Crystal Reports.
To enable read/write access to shared folders on your RMS server we recommend sharing the Microsoft Retail Management System folder as MRMS on your server. Make sure network users are allowed to write to this folder (and sub-folders). Once write-access has been enabled, run the DRS installer again.