Install Thunderbird wherever you wish. The initial profile is placed on drive c: Exit thunderbird and COPY the new empty profile to the desired drive. Restart thunderbird and change location of profile to new location. Now you can create desired email accounts and they will be on the separate drive. As an aside, Thunderbird determines where to look for profile by reading a small text file on drive c that points to the active profile. That file is c:\users\<yourid>\appdata\roaming\thunderbird\profile.ini.

Thank you David. I was able to install the 64 bit version clean. I then renamed a profile from Default and opened a file with the same name on a large data drive. Created the email accounts and everything was then added to that drive. I took less than two hours to get Thunderbird up and running. I must say I spent the last several days trying to get the email accounts off the C system drive as the very large email accounts filled it up. Maybe this can be worked on in a separate of simpler way. I must say I have been a huge fan of Thunderbird over the las 10+ years for both personal as well as business email. I appreciate all the efforts you guys invest!!!! RJ

I'm pleased all worked out okay.