I've got one of the variants of an HP Envy. There's a long rubber foot on the underside of the computer, which covers up a few of the screws to open the bottom.

I've got one of the variants of an HP Envy. There's a long rubber foot on the underside of the computer, which covers up a few of the screws to open the bottom. The problem is that you're going to tear up the strip when removing it (beneath the rubber is a separate, padded adhesive strip that tears easily). Mounting a SATA drive required purchase of some model-specific adapters and a rubber drive caddy. Either the caddy or the adapter came with an extra rubber foot, but I think that each of those parts came out to about $30. Pluses: Individual parts are available to order directly from HP. Once you've identified your machine's exact variant, you can get the service manual and replacement part numbers. The actual disassembly+reassembly was (in my case, at least), really easy, with just a few screws. Minuses: The parts are expensive, model-specific, the correct model number is sometimes confusing to find. Opening the machine can be a destructive operation, for some models. Internal connections don't always use standard interfaces. Close to every model seems to have customized parts, and there are a lot of model variations, so finding second-hand replacement parts is difficult. As seems to be the usual trend, I'm sure that the business models would be a better experience and the consumer models would be worse.