I'd like to set up parental controls for a non-admin Vista user but still allow them to perform installations without requiring an admin password. How can I do this?
You cannot do this easily, applications need administrative rights to install usually, as they need to modify the file system.
If your application users an MSI installer to install (which most do), you can force the installer to always install with admin privilages. To do so you need to make a change in group policy, if the machine is on a domain, or the local security policy if it is not, to enabel the 'Always install with elevated privileges' option in both the machine and the user configurations.