Moving the Windows 7 hard disk from one machine to another

the drivers in use are completely different between your old computer and the new one. You can plug it in and turn it on, but be prepared to spend a lot of time updating drivers, if it works at all. you should try booting into safe mode first, and then update your chipset drivers first. HP should have a list of drivers for your machine and the order to install them.

I've never been successful in swapping harddrives around for the issues Nathan mentions above... If you're unsuccessful swapping HDDs out like that, you could mount the old HDD in an external caddy and get your data off that way, but that won't solve the issues with your installed apps :/