Here is a post from Shaun that I believe will help you locate what you need.
Hey Shaun, sorry to be dense and late on the wagon, but I'm finally home long enough to try and install CE. I'm still running 1.51. Do I first need to UNINSTALL 1.51, then re-install CE (from v1 to v4)? Or, can I install ON TOP of my current 1.51 install (in other words, into the same folder) - in this case, your latest instructions suggest I install the full CE2, then patch w/ CE4? Or....should I leave v1.51 untouched, and install CE to a different folder? (then I'd go from v1 to v4).
I *THINK* the middle option is the right answer, but I'm not doing anything until I hear from Shaun or one of the mavens here!
Install them all to the same folder, the CE releases are simply updates to PS 2007. Here is the process:
1. Install 1.51
Download 1.51 Here
2. Install the PureSim CE2 Full Patch
Download PureSim CE 2 Full Install
3. Download the latest CE patch
Download PureSim CE 5 Patch
At that point you'll be up to date with the latest and greatest PureSim 2007 CE 5 release.