Everything new? Do I need to reinstall OS

[Yoh]

I plan on buying all new hardware, new case, motherboard, CPU, video card, etc. Can I keep my old HDD, cause its got all my games and movies, and the OS on it? Or would the OS conflict cause it's configured to the old hardware?

 

[Cromewell]

You can keep the drive but the OS will probably need to be reinstalled. You can try running a repair install if it doesn't work by just connecting it.

 

[StrangleHold]

I have done this, before you change the harddrive, uninstall your drivers for, chipset, video, sound then go into your device manager and uninstall your IDE channels and Sata if it has Sata and shut down. Boot up in the new system in normal mode and since theres no conflict now with the wrong chipset drivers installed it might boot and windows will install its generic drivers, then you just install all your new drivers. But if not you can just do like Cromewell said do a repair install.