[dheera]

I have a T440p laptop which opens up very nicely and cleanly for user hard drive replacement. 2 screws and the whole back cover pops off, no "warranty void" stickers or any of that. I also upgraded the WiFi module to one that supports 5 GHz, and upgraded the RAM to 16GB, all without any fuss from the chassis. It was significantly cheaper to order the barebones system and do these upgrades myself than to order a more advanced system pre-assembled from Lenovo.

So I don't think changing a hard drive would void it. But also, I don't usually care about warranties. Things usually break only after the warranty expires, and for any electronic device, as long as it's a common enough model number it's usually possible to get spare parts on eBay when the time comes.