Short answer: No.
Long answer: You should not do that, and it depends per application you have installed. Windows .msi installers keep a copy of the installer in this folder. This way it is easier to repair or re-install applications that break (or you consider broken) along the way.
Plus, when you remove an application from Windows, Windows requires to use its installer to remove the software, else Windows won't be able to do this. And it is not a given that a .msi installer is removed from the C:\WINDOWS\Installer folder.
Some (but not all) applications actually require their installer to be in this folder for their maintenance routines. And when those installers are not there, things will go wrong.
To my limited knowledge, .exe installers do not behave this way. As a result you can only install or remove software installations created this type of installers, no repair or maintenance is possible.
Making things worse, Windows and Office updates/patches are also stored in this folder. So you have to be really careful what you can remove from this folder, else you will be in serious trouble very quick. Unfortunately there aren't many tools that can help you identify which files could possibly be removed from the C:\Windows\installer folder.
So, if storage space is an issue on your C: partition, I would move the content from this folder to a folder on a different partition in small sets. This way, when something in your Windows setup breaks, you won't have to wade through lots of files to find the problematic one.
The short answer sounds better by now, doesn't it?
*Edit:
Apparently you can free up space, according to this
blog entry of Scott Hanselman.
