Notes about the SP4 file extension:
Incorrect file associations could be the result of underlying issues within your PC system. As such it is highly recommended to scan your PC for invalid registry entries, unused processes and other unfavourable system settings to identify slowdown issues.
The SP4 file type is primarily associated with '20-20 CAP Studio' by 20-20 Technologies. A program for AutoCAD-based space planning and specification. Default location for these files is My Documents\CAP\Projects.