When installing Titanium Studio as a standard user, the user is prompted for the Administrator password. Having provided it, the files are installed to a user profile, meaning that it is inaccessible to other accounts on the same system.
It is my view that it should not be necessary to install Titanium for each and every user on a system. Hence, the program files should be installed in C:\Program Files (x86)\Titanium Studio, to save 150MB for each additional account. Furthermore, the user should be prompted for the admin password for any updates to that directory (to SDKs and TiStudio itself).
Be aware of Eclipse Bug 249133 that may render this request impractical at this time.