Why is Windows 7 eating up my hard drive space?

Your problem is mentioned when I search with Google. Are you using Explorer PRO:

http://www.cloudberrylab.com/amazon-s3-explorer-pro-cloudfront-IAM.aspx

They may relate to something you are downloading like video?

Download and install cCleaner. A better programme than Disk CleanUp is cCleaner. cCleaner comes with a Registry tool. Do not use this tool as like any registry cleaner it can lead to the creation of very difficult to resolve system errors.

http://www.ccleaner.com/download

1.9. When you open cCleaner you will see four large icons to the left of the window. These are Cleaner, Registry, Tools, and Options. For routine maintenance you would normally access Cleaner (this is not the Registry Cleaner mentioned later). When using for the first time you can just accept the default settings.

1.10. Some comments on settings. On my computer I do not have boxes before Saved Passwords selected. In a less secure environment you might check this option and set cCleaner to automatically run on starting the computer. You may also not want to check boxes before Start Menu Shortcuts, Desktop Shortcuts and Autocomplete Form History. You need to check the boxes to suit your requirements. Getting options wrong first time causes irritants not disasters.

1.11. The second icon you see when you open cCleaner is Registry. One reservation many experienced users have regarding cCleaner is that it comes with a Registry Cleaner. This tool should not be used. Using a Registry Cleaner, however good it is, provides negligible benefits and there is always the risk of creating insoluble system errors, which can only be resolved by reinstalling the operating system and all that entails. You avoid any possible problems by not clicking on the Registry icon.

1.12 The third icon you see when you open cCleaner is Tools. If you click on this icon it gives you access to further routine maintenance options. The first two tools are Uninstall and Startup. I do not use these Tools, preferring to use other software options. The third Tool is System Restore, which is covered in the next paragraph. The fourth tool is Drive Wiper and you will find comments on this Tool later

1.13 Removing System Restore points can be important if you have limited free disk space. The ability to remove them is one of the Tools options. You can selectively remove those created at less important times. This makes it easier to hold restore points for longer periods without retaining large unwanted files, which the inflexible approach adopted by Disk CleanUp fails to offer.

1.14. You cannot remove the latest restore point using Disk CleanUp or cCleaner. If the latest restore point contains malware you can turn off and then turn system restore back on. This has the disadvantage that all restore points are removed when you may wish to retain older restore points that are not infected. The way to get round this problem is to create a new restore point when you are satisfied your computer is free of malware and then remove the infected restore point.

1.15. In normal circumstances you most likely will rarely need to use Driver Wiper. However, there are some situations like if you were giving the computer to someone else, then the Tool might be useful. Please note that Drive Wiper, when opened, generates a warning message, which should not be dismissed lightly. Using Drive Wiper for the wrong reason could have serious consequences!

1.16. The fourth icon is labelled Options. A lot of configuration options are available there. You can set cCleaner to run when you boot but remember this will slow the boot. Another setting enables you to include / exclude cookies. Yet another enables named files to be excluded.