Now do you want to BOOT the win7 drive? If so then this should work. Get into the BIOS and put the laptop drive above the normal drive (or plug the laptop drive sata cable into the port used by your current drive, and plug your current drive into another sata port). After booting get on windows update to pick up drivers you are missing.
NOTE: you will make things much easier if you go to the default VGA video driver before on the laptop before you move the drive if you want to boot it.
Note2: You can also get a USB hard disk enclosure, and plug the notebook drive into the HP as a USB device. But file transfers will be slower.