The RUNAS ... trick is very useful, but fyi, there are installers that verify the credentials of the parent task and refuse if it is not an Admin account.
Try the RUNAS and place your data files in the root (ie C:\My Pictures) to allow all users to have access to it
(if you don't, then only the admin will have access at \Docs & Settings\Admin\My Documents\My Pictures).[*]
IF the installer refuses, then you need to actually login to the admin account to complete the install.
[*] You will need to set the <Everyone> group to have the NTFS privs of full control, but that's trivial