moving installed software from C drive to D drive

Clarifications

Copying installed programs to another partition will only end in tears due to the registry entries becoming unconnected, thereby the programs failing to start.

Having said that, not all programs have registry entries but only you would know that - if you can remember how they were originally installed.

Rather than moving programs around, you may find you have programs that are inefficiently occupying HD space - programs that you infrequently (or perhaps, never) use. The deletion of these items may well free up sufficient space for your immediate needs.

Also, if your HD configuration is anything like standard, all your documents, letters, pictures, music, videos etc will be stored on your C: partition. These innocuous files can, over time, amount to a substantial portion of your partition. They can also be moved to the other partition with ease: all that is required being that you alter the search path for their new location.

You might also consider saving them to optical disc (CD or DVD) thereby freeing up space on C: without occupying space on D:.

Bear in mind that any attempt to defragment your partitions will become difficult (if not impossible) should your free space fall below 10%, with 15% being a far safer limit.

Hope this gives you a few ideas.