File Extension SYS stores system settings and variables used by the Windows and MS-DOS operating systems. The information is stored in plain text and is often understandable, i. e., PATH=C:\WINDOWS\SYSTEM32. Two other notable File Extension SYS files are config.sys and msdos.sys.
File extension SYS usually contain executable code for hardware device drivers (for example 1394bus.sys). File extension SYS contain a command to ask for running a certain device or a command that arrange other command in order their command will work in queue as the system should be run. Sys files run in the kernel-mode which is the highest possible privilege on Microsoft Windows systems. This means that errors in these files can cause great harm and data loss.
File Extension SYS sometime can break because of any other system file that interact into system 32 and make this file broken or removed. We called it infect by viruses, user can install antivirus to maintain computer system and data file. System file that is infected by viruses like trojan or rootkits become very hard to remove and better to reinstall windows software again.