This is way more complicated than downloading a new driver. Please do not reply unless you have been through this yourself. First, the compatibility and the solution depend on the multipass printer model. It is always a good idea to identify your equipment specifically when asking for help. My personal experience is with Canon's MultiPASS F30, but my research revealed a widespread problem that Canon is well aware of. There is a good amount of information at the Canon web site, so the advice to go there for updates is correct.
But Canon simply did not achieve robust compatibility with XP, and SP2 revealed the flaws. My F30 worked O.K. under XP both directly connected and across a wireless network, but the MPService monitoring program did not. Installing SP2 resulted in neither computer being able to see the printer. Sure enough, Canon says that MPService loses communication with the printer, puts the blame on various virus protection programs, and provides a software update to download. (Canon has a long list of its printers that won't work with SP2.)
But the software will not load as long as the computer (operating system) does not recognise the printer as attached and operating, which is of course the actual problem. So it's a vicious circle. I had to uninstall SP2 on both computers to restore the MultiPASS. Uninstall worked great, by the way, and the printer works fine. This is not an old printer, and I am disappointed in Canon and/or Microsoft for such poor handling of compatibility issues. "No printer left behind" is about as true as "no child left behind."