Generally installation disks for Laptops (Many Newer ones do not even supply the Disks) are an OEM version and tied to the specific laptop.
If you have the installation disks for the acer you mostly likely could not reinstall vista to the HP. Installation disks for most "store" bought computer are and OEM version that is tied to that computer. It will either just refuse to install, or when you try to enter the KEY it will notify you that the key is incorrect. Drivers would be incorrect, although that could be fixed by reinstalling the correct drivers.