namely circle of 8 and temple+. can i install the game in program files or will that mess things up?

not sure if I got it right what you're asking, but what you do is 1) install ToEE 2) install Co8 and activate it in its launcher 3) download T+ (it's a small distribution, no need to install it actually) and start playing via the T+ .exe

not sure where in all this you'd need more than 1 installation. However, I don't know if Co8's launcher allows you to de-activate it, if it is that what you're after.