Changing dll names

Hello,

I've just upgraded to a new system and am going through the process of getting everything working again. Of course, this has led to all sorts of problems but one is really troubling me.

Seems that I used to have my Guitar Rig 3 called Guitar Rig 64.dll on my old kit (and had a Guitar Rig 32.dll on there as well that was never used). I've tried installing my copy of Guitar Rig 3, which works fine, but I cannot change its name to Guitar Rig 64.dll. Doing so causes Cubase to crash, and Reaper to not recognise the VST. I tried the same thing using Guitar Rig 5, and it worked fine.

I really need to get Guitar Rig 3 back in as Guitar Rig 64 to get some old but very important projects up and running (and then saved in a more sensible state, of course).

Does anyone know:
1. why I cannot rename Guitar Rig 3?
2. how on earth I managed it before? (could this be a win7 vs win8.1 thing?)
3. whether there is any other way to get around this problem?

Many thanks for any help!