Open Question: Upgraded itunes, now wont even open.?

Im using Vista and have been running itunes on it every since i bought this laptop. I kept getting upgrading msgs on itunes and i finally gave in to get itunes 9. The install failed and now i cant even access itunes. I deleted it all and tried again, but it doesnt work. It says Quicktime isnt running, and that itunes files are missing. Please help, i have been trying to restore it all day.