Sticky stuff is oozing into your laptop - how can you get it out without being taken to the cleaners? Simon Bebbington knows
"But I only spilt a drop of coffee on it!" A terrible cry, and one that has heralded more angst for computer users - and profit for the repair industry - than almost any other. Orange juice is the stickiest assassin of all, but any liquid can find its way into the delicate electronic interstices of a computer and kill it dead.

For desktop users this is irritating but rarely disastrous: the keyboard may short-circuit, but can be cleaned out of house for pounds 25 or so. For laptop users, the story is different - below the keypad sits the system board (the machine's heart) and the hard disk, and liquid can short-circuit all three. These, along with the screen, are the most vulnerable parts.

There are other ingenious ways of wrecking a computer, especially a laptop: leaving a pen in the "clamshell" and closing; poking the screen energetically with a pencil. Dropping the machine is another possibility, while slamming shut an over-full briefcase containing a laptop is a good way of shattering the screen. This is particularly serious as the screen tends to be the single most costly part of a laptop.

So what do you do if you have a dead computer? First, see whether it is covered by a warranty. If an external source such as coffee or a pencil caused the damage, then the answer will almost certainly be no. This leads to the crunch decision: should you send it back to the manufacturer, to a dealer or find an independent repairer?

The answer is not straightforward. It is hard to compare repair costs, because different organisations have different pricing policies. You should also watch the effect on your warranty. If your computer is within its warranty period, using the manufacturer to repair the unit will keep the warranty valid. Using an independent repairer will invalidate it, although you will probably be offered a 90-day parts guarantee. That said, independents will often be much cheaper - they are more likely than the manufacturers to search for the cheapest (unbranded) components or to hunt out damaged chips rather than scrap the whole system board.

Manufacturers put their numbers in the operating book, while independent repairers advertise in the trade press, in Loot and sister publications, and in the computer pages of national newspapers.

If you have a laptop, chances are it is a Toshiba, Compaq or IBM, which share almost 60 per cent of the British market, says the market researcher Dataquest. Your first instinct may be to send such a respectable brand back to the manufacturer - but it probably will not arrive there. Toshiba has a small repair workshop, which handles only the trickiest breakdowns. Dealers do most of the repair work, which means you may pay a profit margin on parts to the dealer and to Toshiba. "We try to sell spares at least at cost to us, if not make a bit of money," says Roberta Colbert, Toshiba's PC division customer services manager.

Compaq farms out its repair work to Network Si Group. Mark Parvin, sales manager of Network SI's return-to-base division, says it charges pounds 40 for a quote, which is rolled into the repair cost, and charges pounds 40 an hour labour (all prices are ex-VAT). It is worth finding out the labour rate where possible, as it can vary greatly: Hewlett Packard charges pounds 60 an hour.

Only the owner of an IBM Thinkpad laptop can be fairly sure it will be mended by the company. Thinkpads can go for repair at IBM Service Plus, which charges pounds 119 for labour, regardless of the job. IBM's parts prices tend to be dear, however. The cheapest system board for a Thinkpad is pounds 870, while Toshiba boards start at pounds 200.

Most independent repairers have a fixed price for a quote, which you pay whether or not the machine is mended. West Midlands-based Lasco charges pounds 25 - and will stick to the quote even if it means it loses money. "People like to know in advance how much it's going to cost," says Roger Brook, its managing director.

Jatin Oza, managing director of Macob Systems, says its Tottenham-based subsidiary Rapid Repairs charges pounds 40 for a quote, which includes parts and labour at pounds 40 an hour. He says his firm may not use the same brand as a replacement, but the parts will be of equal or superior quality - and could come cheaper than the original brand.

A possible cut-price solution is to use trainees at the London School of Computing. Kumar Kandiah, service engineer at the the LSC, says it charges pounds 65 plus parts, which LSC sources from the manufacturers. It will not repair laptop screens, however.

A final tip. Send the machine by courier service, in a box packed with polystyrene chips or bubble wrap about 5cm thick.

Toshiba, 01932 828828; Compaq, 0121 541 4577; IBM Service Plus, 01705 564241; Lasco, 0121 424 5700; LSC, 0171 328 9966; Rapid Repairs, 0181 881 3050.