Most of the new laptop nowadays come with SSD installed. SSD is Solid State Storage which is much faster than the traditional optical Hard Disk Drive. Even the entry-level SSD like the WD Green has Read speeds of 545 Mb/s which is very fast.
The old laptops and even the cheaper laptops come with an optical drive and not SSD for decreasing cost. The most sensible upgrade is first the RAM which if you have an extra slot will be very easy of which I have made a YouTube video.
The laptop will make use of the RAM for performance but still, the laptop will feel slow to boot and launching software. This time the bottleneck is the read speeds of the drive where the software are installed. The old laptops will have a DVD drive which is essentially a SATA interface which is the same interface required for an SSD. But there will be no mounting system. This can be easily solved by a hard drive caddy which is the same size as the DVD drive and fits in the place.
The SSD with the SATA interface fits in the caddy and the caddy goes in the place of your old optical drive. Then the cover of the old DVD drive can be removed and fitted on the caddy which will blend with the laptop and no one will be able to tell if anything is different with the laptop.
Advantages of SSD
1. Boot speed of the laptop will increase leaps and bounds.
2. The software installed on the SSD will launch very fast.
Remember:
1. Old laptop upgrade by replacing the DVD drive buy the SATA SSD and Caddy
2. New laptops buy M.2 SSD
3. The caddy comes in two thickness 12.7mm(very old laptops) and 9.5mm. Check before buying.
