Notes about the SOURCES 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 SOURCES file type is primarily associated with 'Squeak'. Squeak is a Smalltalk based programming language that uses .IMAGE files and .CHANGES files to keep track of user code.