I had a similar experience trying to install the original (v1.1) on Windows 7 (I have an NV+ which is apparently not supported with Photos II). Install got about 95% done then crapped out. Uninstall wouldn't work. No "install.log" was created (sorry, Minerva). Here's what worked for me tonight to install it:
1. I did a System Restore (ALWAYS create a restore point before installing new software, just in case)
2. I deleted the C:\dekoh directory
3. I downloaded and saved (without running) the installer from http://www.readynas.com/?page_id=61
4. BEFORE running the installer, I right clicked on properties, went into compatabilty options, and changed compatabilty mode to Windows XP Service Pack 3.
5. I ran the installer again. I thought it had hung at the same place, but after about 20 seconds, viola, the install completed!
I was fortunate enough to have another PC in the house with XP. It successfully installed the first time (though it failed to create icons to run it - had to manually run C:\dekoh\bin\readynas.exe to create those). Everything seems to be working on that machine.