Opening old projects... did I do something wrong way back then?

My goodness... what a terrible mess this is... I am in the process of opening and working on some old projects. Right now I have Sonar 8.5 PE on Windows 7, all 64 bit. Opening old projects, made with Sonar 6 PE and 7 PE on a 32 bit system, sucks. So I decided to reinstall Sonar 7 32 bit on my system... together with all kinds of old VST(i)'s I had been using way back then. But even this results in a mess... A lot of the routing (to VSTi's) is wrong: I have to reassign a lot of tracks. Some VST(i)'s aren't recognized. Various instruments give me different sounds. Etc. etc. It's IMPOSSIBLE to make the project sound as the wav file I created when I finished the project a few years ago...

I wonder if I had been doing something wrong a few years back or is this what everyone else is experiencing when trying to work on older projects...? It's HELL. I am not only talking about Sonar here, but also all kinds of VST's etc. New versions of software can be nice, but after a few years it's almost impossible to open old stuff...!!! All this makes me think to NOT get X1 or ANY other upgrade to any other plugin... I am already glad that a lot of the projects were made with the same FA-66 and that I didn't buy something new for that in the meantime...

What is your way of handling (and preventing!) all this...?