1. I'd try reinstalling with the anti-virus software turned off. Occasionally AVs kick some program components that they don't get installed.
2. My best bet is... there can be small system file corruptions. Try sfc /scannow from command prompt, better yet a clean install of the OS if you havent' done that since the 7 launch two years ago and have installed / uninstalled / reinstalled numerous programs along the way.
3. Scan the RAM for defects with memtest (make sure to use a 64-bit memtest application if you have >4GB RAM) overnight.
If your C drive is a mechanical hard drive, Win7 automatically defrags it by default unless you have manually changed that setting. Defragging an SSD is not recommended..