I cannot say for Giarc.
I know Katramis tried around 4-5 times with deinstall and install. A new folder in D: was created (D:/SOLO) - but still after pressing "install" button client says he cant use this folder.
D: is the only way for Katramis, cause C: doesnt have enough space
Only for all of you I deinstalled the entire game to test it ...
Test failed because download is working perfectly
(Path: D:\Swords of Legends Online)
Do you have a second device to test it there, too (then copy the files on a external drive etc.)?