I reformatted the D: partition on my hard disk from FAT32 to NFTS and it now shows as half the size it was before - from 36.2GB down to 18.1.

Where has the other 18GB gone? It doesn't show as having been moved to any other partition.

What shows up in Disk Management?

Start > Run and enter diskmgmt.msc

Here's the window Digerati.

That appears to be a hidden partition commonly used by PC makers for system recovery. You may have to use something like Partition Magic to gain full use.

Okay, I'll look into that. Thanks.