Try this experimental program for automatically installing .h2drumkit drum kits on Windows:

H2 Drum Kit Installer

I normally use Hydrogen for Unix, but had to help someone using Vista to get it to work.
It's really very simple, much simpler than any of the workarounds I read here.
There is a console window that runs when you launch hyrdogen for windows, and I figured it all out from reading the error messages that came up. I've forgotten the exact paths, but you can read the errors for yourself, and get the needed paths.
The .drumkit files are gzip'd tar archives. Basically it comes down to getting windows versions of gzip and tar and putting them in the hydrogen data folder, in a subdirectory named GNUUtils.
Create a folder named GNUUtils in the hydrogen data folder.
Download gzip.exe and tar.exe. Copy the .exe files to the GNUUtils folder you just made.
Now the install should work nomally, either from internet or local files.

hi all,
please install the latest windows version (hydrogen_0.9.6-snapshot1.exe).
this will fix all problems with drumkits.
also beside many new features you will get a more stable version than the old 0.9.4 experimental version.
read more here:
http://www.hydrogen-music.org/forum/?action=show_thread&thread=1277&fid=6&page=1
download the current version here:
http://sourceforge.net/projects/hydrogen/files/Hydrogen/0.9.6%20Binaries/hydrogen_0.9.6-snapshot1.exe/download

Hi Wolke

Many thanks for this. I installed the new version on windows 7.
How do I find/install the extra drumkits now?

Many thanks

Paul

main menu->instruments->Import library

then press the update list button and install drumkits as you want.
to install local drumkits just go to the tab "Local file".