I tried to upgrade the BOINC client on one of my Windows 7 x64 machines to the current client, v7.16.7. This has worked perfectly on other Win 7 x64 boxes and on one with XP x64.
I stopped the BOINC service manually on each machine before running the upgrade.
I was initially accessing the machine being upgraded using a VNC viewer, and the installer .exe was on the viewing host. No improvement was gained by operating the machine locally, as I am doing now.

The installer got past "uncompressing BOINC.msi" etc but then got stuck with a popup saying "The file 'C:\Windows\Downloaded Installations\{gobbledegook}\BOINC.msi' is not a valis installation package for the product BOINC. Try to find the installation package 'BOINC.msi' in a folder from which you can install BOINC". I found the BOINC.msi file and pointed the installer popup at it, but it still whinged that this file was not usable. When I quit the installer, it reported Error 1706. I then used Windows explorer to go to the directory containing BOINC.msi and ran it direct. The error popup happens again, but now the message is "The feature you are trying to use is on a CD-ROM or other removable disk that is not available" and the text box is pre-filled with just "1".
I tried uninstalling the old version from Control Panel and the entry disappeared, but the BOINC program binaries were still in place. I deleted them manually. No joy. I ran Wise Registry cleaner. No joy. I ran Iobit uninstaller, which showed BOINC as still installed until it supposedly uninstalled it. No joy. I downloaded and tried to install the 32-bit version 7.14.2. No joy. When I try the 64-bit installer, it still remembers that I had a server install, plus the non-default BOINC data directory. How do I get rid of every trace of the previous installation(s)? Are there installer log files? Where do I go from here?

Software as unreliable as this is surely not ready to be deployed en mass by a company like IBM.