We are unable to install new internet explorer 8-9?

Hi, I hope someone can help me with this one. 1 of the guys at my work has got a "lenovo R61" laptop. The guy asked me to have a look at it for him as it was very slow. I ended up fixing the problem but found something else. He has got a 160GB hard drive in the laptop. If I right click on his drive in "My Computer" it shows "122GB - Used Space" and "20.6GB - Free Space". Now the problem is that he removed all his personal items from his laptop to free up space. If I go to "My Computer" and open his "C drive", highlight everything in "C drive" and select properties to view the size of all the content it only shows "45.8GB". I opened "Disk Management" and found that there is an extra partition on the drive for the "Lenovo ThinkVantage" backups but it has only got a capacity of "5.54GB". If I work it out more or less then about +/- 80GB is used but there is no files listed. The Recycle Bin is empty. There is no hidden files that is bigger than 1GB. What is using the free space?    Please Help

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