Syncing to two PC's
 

I have a 4 year old HP PC that runs XP. I recently got a new Lenovo laptop that runs Vista. Can / how do I sync to both PC's? I'm afraid that if I just sync it to the new one, I'll lose everything and have to start from scratch again. Not a huge problem, but one I'd like to avoid if possible.

that's not the way the sync program works... it "shares" information by default.

If you go to Active Sync in your Programs and then go to Menu -> Options -> Settings, there is an option that says "if there is a conflict:"

and then there is a drop down where you can choose the option to "Keep the item on my device"

But keep in mind, the system requirements for AS 4.5 do not say anything about Vista. This is why some people have issues with it working on Vista (although some people do get it to work). So good luck.