This article is in association withDabs.com

If you're looking for a PC upgrade that will have a dramatic effect, then nothing will deliver quite such immediately obvious results as a hard drive upgrade.

Boot times should fall dramatically, for instance. Your system startup is heavily dependent on your hard drive as Windows and your apps are loaded into RAM, and moving to a solid state drive could see your PC fire up in half the time that it does now.

Apps will launch more quickly, too. Anything that makes heavy use of the drive will run faster; you should find it easier to run multiple applications at the same time; and if you're currently short on hard drive space, then a 1TB drive (1,000 GB) could be yours from under £50.

And of course a bigger hard drive means you can store more stuff on it.

There are a whole host of affordable hard drives around, too. Which is the best hard drive for you? It all depends on your needs.

Performance

If you'd like your new drive to be both spacious and fast then the best option is to buy a conventional hard drive. The capacity of whatever you're looking at will be plain, but performance is less obvious, however there are several indicators you can look for that will give you a general idea.

Mechanical hard drives store data on platters, for instance, circular discs that rotate at high speed. The quicker they spin, the faster the drive is likely to be. A few 3.5" desktop drives have spindle speeds of 5,400 rpm; most run at 7,200 rpm for better performance; some work at 10,000 rpm, usually delivering great speeds but at significantly higher cost.

Another factor is the "areal density" used by a drive, the amount of data it can squeeze onto a platter. The higher this is, the more data a drive can read or write for a given mechanical movement, and the faster it is likely to be.

To compare the areal density of drives, just check their specification and divide capacity by the number of platters. So most 2TB hard drives use four platters, for instance, 500GB per platter; but Samsung's new EcoGreen F4EG requires only three platters, each holding 667MB, giving it a natural performance advantage.

Hard drives will also have an amount of cache memory (typically 32MB although 64MB caches are becoming more common), where they store frequently required data. It's quicker to fetch information from cache than the platter, so the more memory a drive has, the better.

And every drive has a host of low-level statistics surrounding it, but a particularly important one to check is the seek time, the average time it takes for the drive heads to move to a required location. As with all of these comparisons, a lower seek time doesn't guarantee better performance - it's not as simple as that - but it will give you a general indicator of how fast the drive should be.

The 1TB Western Digital Caviar Black can be yours for under £70

Read our Western Digital Caviar Black review

The Western Digital Caviar Green is a conventional hard drive with a very exceptional capacity, an amazing 2TB

Read our Western Digital Caviar Green review

Solid State Drives

If performance is your absolute highest priority, then you may want to forget about old-style mechanical technology and buy a solid state drive (SSD), instead. This replaces the spinning platters with fast flash memory, which has all kinds of advantages.

There's no annoying seek-time delays, for example. A fast 7,200rpm drive might take 13ms to locate a particular item of data, but an SSD should be closer to 0.1ms.

Read and write speeds are also faster, though not to such a dramatic extent. (You probably won't see any real-life task run much more than twice the speed it did before.)

SSDs are also silent, generally use less power, and also run much cooler than hard drives, so you may find your system fan doesn't have to spin quite so hard, or often.

Sounds great, right? But there are problems. Flash memory is relatively expensive, which means SSDs typically have low capacities and high prices. You can buy a standard 1TB hard drive for under £50, for instance: a much smaller 120GB SSD will typically cost you £200 to £300, so perhaps six times the price.

And SSDs have shorter lives, too - the memory effectively wears out with repeated use. There are technologies to minimise this, and you shouldn't see any issues for years, but it's still a concern.

If you can afford one, though, a quality SSD is definitely worth buying. Install Windows and a few important applications on it, leave everything else on a regular hard drive and you'll still notice the difference - it's the perfect addition to a power PC.

To compare SSDs for performance, look for figures like maximum read and write speeds, maximum sustained write speeds, perhaps the number of IOPS (input/ output operations per second). SSDs are particularly prone to odd controller issues, though, so in-depth testing of a drive is essential to find out how it really behaves. Be sure to check out our hard drive reviews to discover which SSDs are worth every penny of their premium price.

The Kingston SSDNow V Series 30GB drives are relatively cheap, perfect for a RAID setup

Read our Kingston SSDNow V Series review

It's an incredibly fast SSD, but the OCZ Vertex 2 delivered only 120GB for a launch price of £264

Read our OCZ Vertex 2 review

Read our group test of the 12 best solid state drives

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