Forget cyberaquariums, starry nights or pictures of Elvis. Oxford scientists are appealing for computer users to donate screensaver time in a search for potential cancer cures.

Oxford University's department of chemistry hopes thousands of people who leave their computers on when not in use will install a different kind of screensaver that can do molecular research.

To neutralise a virus or block a tumour, a molecule of a drug has to lock into a human protein.

Scientists can test the drugs as 3-D shapes on a screen. The catch is that there are 250m molecules to sift.

"To test those crudely, even using supercomputers, would take more than a lifetime," said Professor Graham Richards of the centre for drug discovery at Oxford. "But if you string together a million personal computers you would have enormous computing power."

Oxford scientists have developed a computer tool called Think, and will send anyone who volunteers for the scheme an initial cyberpackage of 100 molecules and a cyberprotein known to be involved in cancer.

Office workers use only about 20% of the power in their computers. The rest could be harnessed for cancer research, with a self-organising programme which quietly sends back to Oxford those molecules that look promising.