Lab

PATA hard disks

Pundits predict that solid-state flash memory disks will replace traditional internal hard disks inside our computers, as they are faster, more reliable and less power hungry. This is unlikely to happen any time soon, though, as a 16GB solid state disk can cost as much as £280.

Hard disks are still the fastest and cheapest way of storing large quantities of data. It's remarkably easy to run out of space on what once seemed to be a massive hard disk, whether you're an avid photographer, a keen home movie editor or you just like playing games.

Luckily internal hard disks are now cheaper than ever, and can store as much as 1TB, or around 1,000GB, of data. The vast number of models can be baffling, so we've gathered together 18 disks and put them through a set of demanding tests to see which are the best buys.

Choosing an internal hard disk for your PC can be confusing thanks to the endless number of models and their jargon-filled lists of specifications. Our buying guide will highlight the issues you should consider before purchasing a disk.

When Sata's day comes

Internal hard disks connect to your PC using either Serial ATA (SATA) or the older Parallel ATA (PATA) interface. If you have an older PC with no free SATA ports, go for a PATA disk. If you have only SATA connectors, choose a SATA disk.

If your motherboard has both SATA and PATA ports available, you could choose either. SATA disks are easier to install, as their cables are thinner and easier to manage than the thick ribbon cables on PATA disks.

Bear in mind that manufacturers are phasing out PATA in favour of SATA, and large-capacity disks, such as the 1TB models here, will be available only in SATA versions. Some newer motherboards also lack PATA ports or can no longer boot Windows from a PATA disk.

The most recent version of PATA has a maximum speed of 133MB/s, whereas the latest version of SATA has a top speed of 300MB/s. These are theoretical speeds which you're unlikely to achieve in practice, but the best SATA disks still tend to be quicker than their PATA counterparts.

If you want to use SATA disks but your motherboard supports only PATA, you can add SATA ports to your PC by buying a PCI adaptor card for as little as £25.

Speed data

Once you've decided between a PATA or SATA model, you must ensure that your computer is compatible with your new disk. The original SATA I standard supported speeds of up to 150MB/s. The updated SATA II standard supports speeds up to 300MB/s. All the SATA disks in our round-up support SATA II and will work at this faster speed if possible.

Check the documentation that came with your computer or motherboard to see which version of SATA it supports. If your motherboard supports only SATA I, SATA II disks will still work, but at only 150MB/s. SATA II disks may require you to set a jumper pin on the back of the disk, telling it to operate at the slower speed. You should do this before installing the disk, and you should check the documentation for your computer or motherboard to see which version of SATA it supports.

PATA disks have a different compatibility issue. Some older PCs have trouble recognising PATA disks larger than 137GB. If you're using Windows 2000 or later, installing the latest Service Pack and updates should solve this. Otherwise, you may need to update your motherboard's BIOS. For more details about this problem, see www.seagate.com/support/kb/disc/tp/137gb.pdf.

Power up

It's easy to forget that your PC's power supply must have the appropriate connector to power your disk. PATA disks use a standard four-pin Molex power cable. SATA disks use the newer SATA power connector, which is thinner than a Molex plug and is easier to unplug. If your power supply doesn't have any SATA power connectors, you can buy a Molex-to-SATA converter for £4 (part code A12AZ) from www.maplin.co.uk.

The price is right

The less a hard disk costs per gigabyte, the more you get for your money. In this month's Labs, we found that 500GB and 750GB disks have the lowest costs per gigabyte. Smaller- and larger-capacity models don't tend to be as good value.

If you need more than 750GB of storage but don't want to buy larger but less cost-effective disks, you could join two or more disks together as a RAID array (see Upgrade Workshop, Shopper 225). If your PC doesn't support RAID, you can buy a PCI RAID controller card for £30.

If you're just after more storage, the best bet is to buy the largest hard disk you can afford. If you're doing certain jobs, such as video editing, performance is crucial - our graphs on page 102 tell you which disks are the quickest.