HP ProBook 6550B 160GB 2.5" SATA Hard Drive with Caddy, Win 7 Pro 64-Bit and Drivers Installed Preinstalled Operating System: Windows 7 Professional 64-Bit Comes with instructions on how to install hard drive and activate with your product key Most Common Drivers Installed, Alternative Drivers Saved on HD Picture is representative only - hard drive make and model varies but will match specifications stated in the listing. Buyer must have a Product Key for the installed operating system