If you regularly move and copy files your hard drive slowly gets fragmented. Pieces of space should, if possible, be close together to make the file access quicker. Try this free defrag software for Windows 7 to see if your system is fragmented and defrag it if necessary.
You can make Defraggler run the defrag procedure while you’re asleep so that you will wake up and access a faster and quicker system than before.
Download Free Defrag Software