Not able to make a second install

[Kival]

Ok, perhaps I should try to explain again. Sorry for my english...

I've a working old installation with various modifications (nonetheless sometimes the script seems not to work properly...) and playing it with the alex.exe. So I do not need the old ROME-CD here. I just need an additional installation for multiplayer purposes. Copying the old rome-data does not work because of the different cd-keys (?) so I think I've to make a new installation with my new ROME-GOLD version. Therefore I seems as if i must edit the registry because I do not really wish to uninstall my old installation. I'm happy to have a working version on Vista 64 bit. But I'd like to know if it is possible to clean the registry without doing any damage to the old installation. You're not sure about it and I do not know enough about the registry to make at least an educated guess.

EDIT: Wait, i got it, if i make a backup i can try and see. Good idea.