One of the best tool under windows is TortoiseGit. It integrates tightly with Explorer so you don't need to use a separate application or use command line tools. In order to use it, you will need to download and install 2 components:
If you have access to push to the repository, you will need the Git Credential Manager for Windows to store credentials and avoir having to re-enter them everytime. Before installing, insure you have git.exe in your system's PATH (i.e: C:\Program Files\Git\bin). Download the installer and run it. If the installer complains it can find Git, restarting windows should solve the problem.
After installation, the fist time you try to push, tortoise git will ask for credentials. After that they will automagically be stored in WIndows credential vault and used for subsequent pushes.
To be re-written(move to GIT from Google Code, linux user please update)