I can't load TomTom3 onto my PC

I have searched the posts to see if this question has been asked before and I can't find it, but if it has I do appologise.
I have just bought TomTom3 and I am having problems installing it onto my PC. I keep getting the message.." Your PC does not support the devices for which there are applications in this package. Please install the supporting software first and run setup again.".. I carried out a search on Google and found an update on the TomTom website but this did not work. Have you any ideas as to how I can resolve this.
I appreciate any help you can give me.