Internal drive Pounds 549, external drive Pounds 649. Add the following if required: small computer system interface card (SCSI) for PC Pounds 50, for Acorn Pounds 150 (no card required for Apple); 650 megabytes optical disc Pounds 39. From Cumana, Pines Trading Estate, Broad Street, Guildford, Surrey, GU3 3BH. Tel 01483 503121.

There’s a condition called Obsessional Hard Disc Pruning disease. It’s caused by a chronic shortage of hard-disc space and leads teachers to wipe out huge amounts of pupils’ work (usually art or multimedia) and suffer pangs of guilt. Cumana’s proTeus is a new storage solution that could be a cure.

The proTeus disc drive takes an oversized floppy which can store 650 megabytes of files enough to copy an average hard disc. Remove the floppy, drop in another and you’ve got another 650 megabytes of breathing space. These phase-change optical discs cost just Pounds 39 each.

The proTeus can also read ordinary CD-Rom discs using a simple, dual-purpose tray. This is a quad-speed CD-Rom drive which means it works a bit faster than a double-speed drive.

For a tidy set-up the unit can be fitted into a bay inside the computer and connected to an SCSI card. An external model costs more but can be shared between computers. Apple users are at an advantage as their machines have the SCSI feature as standard. Others will need a second SCSI connector.

The proTeus drive seems fast enough to store and run programs. It’s when you save your work that you notice speed difference: my initial tests showed it to be half as fast as a hard disc. That was using a single, large file; when I saved lots of small files it was five times slower than my hard disc.

Even so, when you are paying just six pence for each megabyte of storage (which is less than ordinary, magnetic floppies) this system is very hard to dismiss. If you can see yourself needing only four discs, you’ve probably made on the deal and you’ll never need to prune so ruthlessly again.