Same issue as under vista. What all the great fixing tutorials fail to tell you is that you need to register your DLL in another directory for the x64 verison.

1. press windows key, enter cmd into the text field, wait for cmd to come up, right click it and select “run as admin”
2. cd to your windows directory
3. cd to your system 32/64 directory:

x32: system32
x64: sysWOW64

4. enter:

regsvr32 jscript.dll

And suddenly it installs again.