I would share it through wifi instead of bluetooth. You'll have better range and all around better support/functionality, but you shouldn't have to remove the dongle, just connect over the network rather than directly via bluetooth when setting up the printer on his laptop.
How old is this printer? Vista can have trouble with older printers and if this is connected via parallel there may not be a vista driver for it (especially if his laptop is running the x64 version).
Try connecting it through the network if it doesn't show up automatically when adding the network printer from his laptop click "my printer wasn't listed" and manually enter the printer (//server/share name).
OlyComputers
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