Just out of curiosity, why would you want to make two custom directories? Would that prevent possible nasty programs/files from corrupting others in the directory?
Nope not at all, though it can help in some cases, it just helps trace,track and troubleshoot problems
at least in my case anyway....
If a program has a set directory then it will in most cases also install parts to another directory without your knowledge.... by placing an untrusted install in a custom directory i can monitor its behaviors by locating part files in unspecified locations
so even if you install on disc D:// it may very well place parts on C:// regardless of your specified location
An install that requires by default a manual input directory will tend to only install to that set location..... anything by this means will be1 of 2.... 1 very old / 2 badly programed and thus rising suspicions to its safety
Id just say in this case it would be safer to place in an user defined location to be able to monitor the programs behavior