Notes on Gpg4win 3.0 Release
Use Gpg4win with Windows XP and Windows Vista
Unfortunately, the QT-Developers dropped the support for Windows XP and Windows Vista in never Versions, therefore the standard installation of Gpg4win works, but some of the components of Gpg4win won't work out of the box. But there is a Workaround to get Gpg4win fully working on Windows Vista and Windows XP. This is done by choosing GTK-based applications over QT-based applications.
During the installation choose GPA as standard key-manger, instead of Kleopatra.
After the installation, locate the gpg-agent.conf in C:\Users\Your Username\Application Data\gnupg (if it is not there, create it). And locate the "pinentry-gtk2.exe" in your Gpg4win installation Folder. Then add the line
pinentry-program C:\Path\to\pinentry-gtk2.exe
to the gpg-agent.conf and restart your computer.