I am trying to update my 5.2.2 version to the new 6.6.2 version. I've run into the .msi file not found problem. I found the FAQ on that problem and started in on solving it. I stopped because it is getting late. I will give it another go tomorrow.

I've been reading some threads on the new version. I have a question about the data files. My 5.2.2 version has the executable and the data in the same folder (E:\BOINC). I thought to make a new folder for the data before trying to install the 6.6.2. Which files should I copy over to E:\BOINC\Data ?

Also, is the 5.2.2 install available anywhere? I looked on three different pages that had previous versions and could not find anything earlier than 5.4.

DON'T fiddle with new folders and moving files.

The 6.* versions will do all of this for you. Just tell it in the advanced section of the installer if you want to put things in a non-default location.
I created new partitions, and put the programs on d:\ and the data on e:\, with an f:\ partition for saving backups of the climate models.

All (or most) of the older versions are available somewhere, but I forget the url.
Someone will show up with that info.

I made a slight error on the version number. The about box says 5.2.12. I can't find any install files prior to 5.4.x.

I did find a reference to 5.2.12 in this thread
http://boinc.berkeley.edu/dev/forum_thread.php?id=246#1155
but the link to the file returns 404.

I found the install at
http://morel.mit.edu/download/boinc/dl/?C=D%3BO=D
They also have the 4.x versions as well as 5.x.x