Run the following commands in terminal/command line:
move "c:\users\MYUSERNAME\MarketFeeder Pro 7\" "d:\data\"
mklink /d "c:\users\MYUSERNAME\MarketFeeder Pro 7\" "d:\data\MarketFeeder Pro 7\"
Where d:\data\ is your big disk data folder, MYUSERNAME is your login for the computer (not BetFair).
The first command moves your MF pro profiles and data to another HD, second one makes a link to that folder in the usual location.
Please make sure MF pro is not running during this operations.