IDE 4.6 is part of SDP 6.4.1 release, if you using this web site to download and install, it is provided as "experimental" version for evaluation purposes only.
IDE 4.5.1 is a maintenance release of IDE 4.5. Available online only. Can be updated from IDE 4.5 using update size or installing standalone version.
IDE 4.5 is part of SDP 6.4.0 release, if you using this web site to download and install, it is provided as "experimental" version for evaluation purposes only.