I have recently bought an HP SmartCenter computer to replace my 5 year old XP job. I am amazed at how slow it is to do everything - for instance Booting takes about three minutes whereas my old XP took little over one minute. It also often seems to go 'walkabout' when the hard disk gets busy and delays everything. It has been like this from first use. Is it the computer, is it Vista, is it me? I use the paid-up version of AVG and have the Vista firewall enabled, and I never click on adverts or go idly wandering round the web. I like it for its compactness and quietness but I do wish it would get a move on!
Well if it doesn't have a graphics card just onboard graphics i'd disable the aero interface which might make it go a bit quicker, check to see if anything is scanning on boot and do a defrag of your hard drive as well.
Something's wrong - no new machine running Vista should take nearly that long.
anskyber's suggestion is probably on the money - new computers often come with all kinds of manufacturers' software or trial versions of well-known applications, etc. Take a look at what runs at startup and you might find all kinds of things queuing to phone home. Work your way through the list, disabling this, and uninstalling that, until your machine is leaner and much faster.