Harddisk space problem. I have a 240 GB HDD. My C drive has been allotted 58.2 GB of space. The

Question

I have a 240 GB HDD. My C drive has been allotted 58.2 GB of space. The amount of free space showing is 4.78 GB. Other than the Windows and other software( around 5-6 GB max) installed on the PC there is no big file in this drive. The Windows folder in this drive is showing size on disk as 29.0 GB whereas when i open the Windows folder and select all files and folders the total size only comes up to 3.48 GB. This in spite of showing all hidden folders and files. I also cant figure out for what the remaining space is utilized. Please help. Also could anyone give me a link to a software that will show me my entire system properties like name of manufacturer of HDD, various components installed, etc.