Whiz
I have Vista on my "new" PC, and have had no real issues regarding speed, etc, but a quad core processor could have something to do with that. I would turn of Aero (if it is on your version) for starters, and do the usual things like check on the size of the pagefile, graphics settings, ya know the deal.
As far as updating things goes, well, the first thing you should be doing after installing anything from scratch is actually updating it anyway! You should always be going to the manufacturer websites to update drivers (don't use windows update for drivers, it can have "issues"), and always check for updates from every software producer. That applies to any operating system, you would hardly run your firewall/antivirus software without ever updating it and you should do the same for other software. TBH, the only software I had issues with and couldn't replace with something free was a few games, everything else was easily updated for nothing, so you shouldn't have any real issues. If Vista is an issue then you can wipe it out and install XP, and in fact I think Dell could even do the changeover for you as they are still selling computers with XP installed.
BRL:- Have you updated the software? If not, go here
http://software.canon-europe.com/sof...540.asp?model= and download this update. If you have only installed the software from the CD it won't have the Vista drivers there. Go here
http://software.canon-europe.com/products/0010371.asp for all the rest of the stuff you'll need. If you have updated, then the issue could be as simple as the cable you connect with but without seeing it I wouldn't be able to tell.