I've been experiencing this problem for the past few weeks.
I tried installing solidworks 2012 sp 4.0 x64 immediately after reinstalling windows.
I have two issues:
First, when I run setup.exe, I get a white-blank page where the install is supposed to guide you through. This is not the major problem, as I am able to bypass it by directly running setup.exe in the swwi folder.
The major problem: When the install is nearing completion, I get Error 1721, which is associated with sldshellserverexe using the regserver command.
I am using the student edition that I downloaded off my schools website.
Is there anything else I can do?