I just uninstalled InDesign CS6 -- which leaves on my computer InDesign
Some file associations are now not quite working properly (specifically,
for the ExtendScript toolkit).
Is there any way to "fix" an installation of InDesign CS4? (without
having to uninstall and reinstall)
Windows 7 Ult. 64-bit
Try running the installer again without uninstalling first. You should have a "repair" option which MIGHT work, or maybe run System Restore and pick a point before you installed CS6....