That folder contains installers for the software you've installed on your system. You'll need some of those installers to uninstall software. Sometimes, this folder gets cluttered b'coz some installers aren't deleted after the program is uninstalled. To free up some space, do this.
Right click on the partition, hit disk cleanup and clean the disk.
Go to the installer folder. Under the View menu, click on Details. Then click on Choose details in the view menu. Here, tick the Subject box. Click on OK. You'll have to wait for some time for the subjects of all installers to appear.
Now, you can view the subjects of the installers. From the subject, you can understand the program with which the installer is associated to. If there is any installer which is associated with a program you've already uninstalled, right click on the installer and delete it. Don't delete other installers bcoz you'll need them to uninstall your software.