Have you cleaned out your temp internet files, lately?
Certainly worth treying also, I didn't want to give too many instructions in one go. The best way to do so:
Please download CCleaner from here:http://www.ccleaner.com
Before first use, check under Cleaner Settings, Windows and ensure "Empty Recycle Bin", "Temporary Files", "Memory Dumps", "Old Prefetch Data", "Cookies" and "Temporary Internet Files", are checked. Please also go in under Options, Advanced and ensure the box next to "Only delete files in Windows Temp folders older then 48 hours" is 'unchecked'.
Then open it and select any other items you wish to clean up. This will remove any malware hiding in your Temporary Folders as well as freeing up a large amount of disc space