Windows/Installer Folder

I recently work on a Laptop that had a 70gig harddrive. The owner was getting the disk is full error and was puzzled, because he did not have much installed on the harddrive. I checked it out and he did not indeed have anything much installed but the harddrive was showing only 255MB of space left on the 70 gig drive. I could not find any folder with any amount of files it on the C: drive. I removed some unneeded software but only got it to 455 MB of free space. The rest of the Article is here Disk Full.