Welcome to CDF, Jojo8
We need to know a few details - what are your PC specs (specifically, make and model of hard drive/CD-DVD drive(s) etc)?
As the problem seems to occur with defragging/changing directory etc (I assume you mean changing directory on your HDD, not DVD drive), can you see the link in my signature - "How to check/enable DMA" - and check all your drives to make sure the Current Transfer Mode is UDMA Mode?
The two could be connected if your HDD, for example, is running in PIO Mode. But if you can give a few more details and try what I suggested, we'll know one way or the other.