My windows directory is huge
I spare 30G for C:\ for Windows 7. As time goes by Windows fill it up.
I do not know what can be removed. How can this be solved?
The c:\windows folder will grow, however you may want to check
This folder can grow at a faster rate than the windows folders, and it is usually easier to target what is consuming space. For example, if you have lots of music or images you can move them to a different drive.
I find windirstat is a good tool for identifying where space is taken up, and can quickly show large files at a glance.
Don't delete anything unless you are sure it is not critical.