How to transfer from one half of my hard disc to the other side?

I have a 6 year old Sony Pentium 2.8 computer. The hard disc is divided into 2 halves C&D. The C side is nearly full and I am unable to defrag entirely.A lot of the space is taken up by Microsoft security updates. I have been told not to touch these. I have placed a few of my software programmes on the D side. How do I transfer other folders such as Programme Files and Doents and settings from C to D. As simple as possible please as I am of the older generation and not too computer literate. Thanking you in anticipation Charlie