We've been asked about the potential for a G751 upgrade, regarding HDD/SSDs, memory and even replacing the Blu-ray drive. These are user-accessible via a single hatch on the underside and retain the warranty. Further changes require more complete dis-assembly of the G751, and are not recommended (at the very least you lose any remaining warranty), so be sure to check your spec before you buy.
To start, put your G751 on a non-scratch surface and flip it over.
See the tab in the middle, lift it up and reveal the screw underneath. Unscrew and carefully pull away the plastic cover.
Ta-da! In this model we have the M.2 version, but you can also buy a G751 with two HDDs installed. Note the mounting bracket is different for M.2 SSDs (yellow) and 2.5 inch SSDs/HDDs (red). SSD models will be listed "SATA" or "PCIE" in the retail specifications before you purchase. Please purchase a model with "SSD PCIE" listed, otherwise the M.2 bracket cannot be provided for after-sales upgrades sorry.
Here are some close-ups of the first drive bay, where both the M.2 PCI-E x4 slot and SATA ports inhabit. There is no M.2 slot in the second drive bay and M.2 SATA SSDs are not supported, only PCI-E-based (which are better!). M.2 PCI-E SSDs up to 2280 spec (80mm long) can be installed and they are held in by a single retaining screw.
For the 2.5 inch HDD/SDD cage, four screws are required to secure it to the caddy (two are pointed out with red arrows, with two more directly on the opposite side). Pull the tag across to unlock the drive from the SATA connector. A few more screws on the side then to hold in the drive to the caddy.
Two DDR3L (1.35V) SO-DIMMs can be changed out, with two more pre-installed within the unit at time of purchase (highlighted below). Up to 32GB can be installed and if you intend to run this quantity at a later date, be sure to purchase with at least 16GB, so 2x 8GB DIMMs are pre-installed.
The optical drive is retained with a single screw, and the connector is standard SATA:
The battery is non-removable and integrated into the chassis: