u have to have at least 512 mb ram to install it bro. I got a dell dimension pc too with a pentium 4 what dimension is ur pc?
yea go with the upgrade advisor. it sound like (to me) that you should be able to run it on your computer but yea you do need at least 512mb of ram if you dant have which you probably do then upgrade your ram. My opinion i wouldnt upgrade to vista right this moment i think its buggy. what a couple months until they come out with some more updates.good luck.
Most tech people are saying don't upgrade an Xp machine, if you want Vista, get a new machine. If you still want to upgrade at least wait for SP1.