You have less than 10% of available space on that hard drive. It's time to retire it. ASAP.
Back it up and get a new drive, saving two backups of your image files in the process.
Metadata should be preserved and new thumbnails will be generated when you purge the cache, but it can be a time consuming process.
Is that drive also your boot drive? If it is, then you're in a heap of trouble already. A measly 45 GB is not much to be shared by Photoshop's scratch file and the swap files of the OS, let alone to accommodate the cache.