For Half Char- char ्  For क्र - press क ् र   For  र्क - press र ् क
For  द्व - press द ् व   For द्य - press द ् य   For  द्ध - press द ् ध

If 'Hindi Characters' are not visible install Hindi by:-
For Windows XP and Above Versions :-
Control Panel - Regional and Language Options - Languages
Select "Install files for complex script and right-to-left languages"
Now click on 'Details' and add Hindi in Input Language.
For more details drop your query to  ruvimals@gmail.com