Windows 7: Why cant i install files in C

this windows now installs all the files on D drive. example. i cant update my Avira antivir because there is no spave for update in D drive. plz help this installs automatically all the files in D

When you say "now installs all the files on D" when did this first occur; after a Windows Update, after installing some software, after a system crash? Please submit the answer along with the following;

Post a copy of your Disk Manger;
1. In Windows 7 and Windows Vista, click on the Start button.
2. Type the following command in the text box:
diskmgmt.msc
...and then hit the Enter key or press the OK button
3. Follow the instructions below;
Screenshots and Files - Upload and Post in Seven Forums

Yeh, for first.i know why it does this, probably because i accidentally installed windows in both drvies and i was running windows on c drive that moment. and for second i have no idea how to post picture of my disk manager

What part of my post did you fail to understand? I tried to provide the information necessary to post an image; what information do you need?