If you want to upgrade or replace your laptop hard drive, you want to make sure you get one that’s the best fit for your particular laptop, and if you’re not a pro at these sorts of things, make sure you know all the facts before investing in a new hard drive and start taking your laptop apart (we’re talking about an internal hard drive here – check out this post for external hard drives).

So what do you need to know? Here are the main points to consider (for once, we’re not concerned with whether they come in pink or not, since they won’t be visible anyway):

Capacity
Traditional rotating laptop hard drives come in sizes from 20GB to 1TB, and Solid State Drives (SSD) for laptops are available in 8GB to 1TB. Solid State Drives can handle being shaken and dropped, and do not spin, so rpm is not a factor here. Price is though – they are expensive. A 1TB SSD drive costs around $3,000-$4,000+ whereas a Western Digital 1TB hard drive (5400rpm) is around $180! Also, on newer laptops you should be fine installing an SSD, but if your laptop is older and runs on XP, the operating system is not optimized for an SSD and you may experience difficulties with it.

RPM
RPM stands for Revolutions Per Minute and tells you how fast your hard drive spins. 5400rpm is the most common speed in laptop hard drives, but they come in 4200, 7200, 10000 and 15000rpm as well (the two larger numbers are for hard drives you buy separately, there are no laptops on the market with that kind of HDD already installed, not even gaming laptops). The faster they spin, the faster your system operates. However, spinning fast also means consuming more energy (draining the battery) and generating more heat, so that’s something to consider.

Physical Size
This one is obviously very important. Laptop hard drives come in two standard sizes – 1.8″ and 2.5″, with the 2.5 hard drive being the most common. You’ll find the 1.8″ mostly in mini notebooks. However, they also come in different thicknesses. A 12.5mm hard drive will not fit in a laptop that has a 9.5mm slot. Check your manual or call the manufacturer to make sure you know what your laptop needs.

Interface/Connector
Interface means how your hard drive communicates with your laptop and there are two different kinds: SATA (serial ATA) and PATA (parallel ATA a.k.a IDE). You can tell which is which by looking at the hard drive pins – PATA extends out from the body of the hard drive whereas on SATA drives, the pins are more a solid part of the drive. There are also two types of connectors: IDE and ZIF. Check your documentation to see which one your laptop uses.

Cache
The cache is a space on the hard drive that stores data temporarily for fast retrieval. A larger cache can improve the speed of your system, but it’s not the most important factor (rpm is when it comes to speed). In fact, if you go to some of the major manufacturers’ websites and look at the specs for the laptops, the size of the hard drive cache is not even listed. It is though if you’re buying a separate hard drive to install yourself. 8, 16 or 32MB are standard cache sizes.

So is a 750GB 5400rpm hdd better than a 500GB 7200rpm hdd? Better is not the right word: the first drive will store more but be a bit slower and the second drive will store less but work faster. You have to decide what’s most important for you and base your choice on that.