... but XP's Zero Configuration Utility is prone to random disconnections in my experience. I overrode all my network machines so they used the card / adapter utility software after having these problems. A bit of a google showed that it can be an issue.
Will wrack brains to try and remember how to make sure Windows Zero thingie is switched off.
Start - run 'msconfig'. Select the services tab, find and uncheck zero configuration thingy and it'll not load from then on.