The Sony VAIO VGN-SZ4XWN/C (£1699 inc. VAT) is part of the company's ultraportable range and as such, weighs in at a portable 1.8kg.

As a two-spindle machine it features a hard drive as well as an optical drive. This is a great solution for those people who don't want to compromise on power and features when on the move.

The chassis is made of magnesium-alloy with the same material used on the back of the lid to protect the Super-TFT display. The screen is an impressive 13.3-inch panel that uses LED backlit, and images are pin-sharp.

Graphics are handled by the powerful dedicated Nvidia GeForce Go 7400 adapter. The 7400 is a mainstream adapter that handles most applications with ease.

Designed around Intel's Core 2 Duo T7200 chip, this system uses the older 667MHz Front Side Bus, as opposed to the 800MHz of the T7300 chip. Even so, this proved to be a fast and reliable system that ran well. Files loaded quickly, largely due to the addition of 2048MB of memory.

The keyboard spans the width of the chassis with large, squared off keys. They have a comfortable weight and typing is a pleasing experience. The touchpad and mouse buttons are integrated and also include a biometric fingerprint scanner and while they feel less robust than the keyboard, they are still firmly attached.

The VAIO doesn't come with 3G built-in as standard. Instead, Sony ships it with a plug-in card. This works in conjunction with T-Mobile and comes with a free 30-day trial period. After this, you can expect to pay around £45 (inc. VAT) a month for a typical data connection.

The use of a plug-in data card is the most power-hungry form of 3G, as you need to power the card as well as monitor the connection and we found this had a 25 per cent impact on battery life. Under test, we managed to get 147 minutes from the standard battery pack, with this dropping down to 120 minutes with 3G running constantly.

The VAIO is a great laptop for use on the go, but the move to Windows Vista has had an impact on the battery, as it no longer delivers the lifespan it formally did. To help preserve battery life, there is a Stamina switch, which drops the CPU and graphics processor speeds to half and dims the screen.

Overall, the Sony VAIO VGN-SZ4XWN/C is something of a mixed bag; it's a powerful performer that handles all tasks with ease, but suffers from a less than ideal battery life.