I just did this recently and followed the instructions provided by the good folks at Adobe:
Thank you for contacting Adobe® Web Support for assistance with Adobe
Photoshop Lightroom 1.2®
I understand that you want to know the best way to install Lightroom on
the Microsoft Windows Vista Business computer you will be upgrading to.
Because the updates have added compatibility fixes for Vista as well as
other fixes and changes, the best thing to do is install directly from
the 1.2 update installer on your new computer. You do not need
to install the earlier versions first, and the same serial number should
work. The update is available on our website:
http://www.adobe.com/support/downloads/detail.jsp?ftpID=3728It would be a good idea to make sure you have the same version installed
on your existing computer so any database updates are done before you
transfer to the new one.
I also understand that you want to know the best way to transfer your
catalog and images to the new computer.
The best way to do this in Lightroom 1.2 is to use File > Export as
Catalog. You can select a new folder to export to, and you can include
the #negative# files which are your original images. It will keep the
same folder structure you have for the images in Lightroom, and those
folders will be copied into the folder you specify for the catalog
export.
You can either copy the folder to the new computer, or if you have the
external hard drive, you can do the export directly to that drive. Once
you have the files copied over or the external drive attached to the
new computer, go to File > Open Catalog to have Lightroom open that
catalog.
I hope this information helps to answer your question.
If you require further assistance with this question, please update your
web case with complete details including what steps you have already
completed and any additional information you feel is
applicable to your question.
You may also call us at (800) 642-3623. We are available from 6:00 am
to 5:00 pm Monday - Friday, Pacific Time.
Kind regards,
Leland B.
Adobe Web Support
Worked fine for me, best wishes