Firstly, I suggest that you fit a Samsung SSD (there two choices, 860 PRO SATA III 2.5 inch or the 860 EVO SATA III 2.5 inch) these come in various capacities ''''''e.g. 500''',''' 1,2 and 4TB, ''''''all these drives come with the Samsung ‘Data Migration’ software and they are very easy to migrate your existing boot drive. The Samsung SSD’s are the quickest and are the best for the Aspire 5750. I’ve got an 860 PRO 1TB and it works unbelievably fast. To fit this new SSD drive do the following: open the back underneath big cover that has 2 screws right underneath where the pointing device is, remove that cover, inside you have the RAM sticks (on the right side) and the WiFi card in the middle, on the left is your existing HDD, pull the existing HDD out (by the attached plastic attachment) and remove it, then, insert the new 2.5 inch SSD drive. Its as simple as that.
'''Note:''' make sure that you have migrated your operating system with the bootable HDD to your SSD drive before changing to your new SSD drive, this is a simple procedure and it shoulde’t take very long to do with the Samsung ‘Data Migration’ software, you need a “USB 3.0 to SATA 2.5" Hard Drive HDD SSD Adapter Converter Cable 22Pin UASP” that you can purchase anywhere. ++++That’s it but, I would also suggest that you run your laptop with 8Gb of RAM (2x4 PS-3 1600MHz) and change your processor to an e.g. a i7-2720QM as the i5 that the 5750 came with are a bit slow, just a suggestion, as that is what I’ve done and the combination above makes the 5750 or 5750G a very quick and usable laptop for the current crop of Windows 10 1809 operating systems.