No need to install net 4.0 as 4.5 supersedes 4.0 so only 1 should be installed. In fact, when it was in RC, when I installed net 4.5, it first removed 4.0 and then installed 4.5. So, just go ahead and install either 4.0 or 4.5 but not both. win 7 has net 3.5 inbuilt and a fresh install will give only updates for 3.5 If you install net 4.0, you will get updates for 4.0 too. With net 4.5, you will not get any updates because it was released only last week. As already noted, win 8 has 4.5 built in.
Use the /quiet parameter with the path of the EXE to make it install silently (will still display the extracting dialog though).