I have done this by making a symlink to another location. Works like a charm.
In a command window you could type this:
ren %appdata%\BurstWallet\burst_db %appdata%\BurstWallet\burst_blockchain
mklink /J %appdata%\BurstWallet\burst_db "D:\Data\Crypto\Burst\Blockchain"
copy %appdata%\BurstWallet\burst_blockchain\*.* %appdata%\BurstWallet\burst_db\*.*
rmdir %appdata%\BurstWallet\burst_blockchain
It renames the current directory holding the blockchain to burst_blockchain,
then creates a symbolic link named bust/db pointing to "D:\Data\Crypto\Burst\Blockchain" (enter your path on another disk here),
then copies the files from the renamed directory to the location used by the symlink,
then deletes the empty burst_bloackchain folder
Enjoy your free space on your system drive :)