Emprex's D250PE Mobile Storage Drive is a casing for a hard disk.

The idea is that you buy a 2.5in hard disk or remove one from an old PC, slot it into the case and use it as an external hard disk.

It was easy to set up, although the hardest part was finding a suitable disk.

The disks it takes are older IDE models, which have largely been replaced by newer Sata ones.

If you're buying a hard disk for the D250PE, then, make sure it's a 2.5in IDE one, while if you intend to use an older disk, make sure first that it's the correct type.

Once we'd found a disk, it was easy to fit, and the software to make the disk ready is easy to use.

It does erase everything on the disk, but it has the advantage of setting the new disk up as secure – meaning that you'll choose a password, and without that the disk can't be accessed.

Here we ran into a problem – while the password software worked fine on Windows XP and Vista, and even Windows 98, it won't work with Macs or Linux computers, negating part of the point of USB, which is its universal compatibility.

Still, if you use only PCs and you have access to an old IDE notebook hard disk, the D250PE is a bargain, available online for under £15.