I haven't got the chance to back it up unfortunately, but i understand that I can back it up manually.
However, I tried to uninstall the app many times and I downloaded the latest version once with "qtum-0.14.13-win32-setup-unsigned.exe" and "qtum-0.14.13-win64-setup-unsigned.exe" but the same problem exists, it just load blocks but no window appears. As @qtum-earlz mentioned, I deleted all the files except wallet.dat and still the same.
The question is, does uninstalling the app affects the wallet.dat? because i notice the file date modifies accordingly but I can see from its properties that it was created along time back at the time I installed it the first time.
Please help me retrieve my qtums it must be there somewhere.