Windows folder is about normal on size for Windows 7 and program files as well.
The one that is on the large side is the users folder. That is where I would look to find out what is taking up to 12 GB. With normal profiles you might have an avg. of 1 to 2 GB.
Also if you have itunes installed that might explain it, when it does a backup of your device those can get very large.
You should think about getting a new drive for the laptop. It will be both bigger and faster. Given the age of the laptop it is an IDE hard drive (Not sata). I just checked newegg.com to give you a link to one and they don't have any ide drives for laptops listed! Man times are changing fast lol
Shane