CAT files are generally Microsoft digital signature files for drivers. Microsoft tests the compatibility and stability of drivers developed by hardware manufacturers (this certification is strict). Drivers that can pass the test will get a digital signature (a. cat file) and issue a Designed for Windows logo. In addition, the HCL list is added to add the driver to the driver. CAB file of Windows installation CD. Drivers installed in users' computers are generally stored in the folder C:\WINDOWS\SYSTEM for Windows 9x/Me systems; For Windows NT/2000/XP, drivers are usually located in the folder C:\WINNT\system32\drivers.