.SY_ File Extension
File TypeCompressed SYS File
What is an SY_ file?
Compressed .SYS file sometimes used by application installers to reduce the size of installation files; similar to a .EX_ or .DL_ file and can be expanded back to a SYS file using the Microsoft Expand command line utility with the following syntax:
expand file.sy_ file.sys
NOTE: SY_ files also may just be renamed SYS files and therefore may not be compressed.