Update: Outlook 2010 stores the download history in the pst-file itself and should not re-download the mails when you configured Outlook to download your mails to your existing pst-file instead of a new one. That is why Outlook starts to download all the messages again.
When starting with a new mail profile (which gets created when you configure your new computer), Outlook is unaware of what has been downloaded already by another mail profile. I have Outlook set to leave a copy on the server but now that I have reconfigured Outlook with my email account, it starts to download all the emails again. I installed Outlook on my new machine and transfered the emails that I had downloaded already.
