KACE Product Support

Do you mean that the software is showing up under Inventory | Software?

If yes: you can delete them there. But if you have linked it to anything you need (License assets, Custom Inventory Rules, Managed Installs etc) you should not do this since you will also loose these items there. 
Overall it is not nessesary. Any software item here was once inventoried (probably the software was upgraded or uninstalled if 0 machines have it installed still) or is manually created.

This is one of those clean up things I do occasionally, like before an upgrade. It isn't necessary, but I do prefer a clean and lean database, when possible. My method is:

1. Open the Inventory, Software page
2. Sort by number of devices, descending
3. Set the page to display 250 items
4. Go to the last page
5. Verify the first item has 0 devices
6. Click the box to select all items
7. Choose action, delete
8. Click yes to confirm deletion
9. Wait for the page to reload
10. Go back to step 4 and repeat until the items with 0 installs are gone

So I figured out how to do this.

Do an Advanced Search for Devices Affected = 0 and Search
All devices with 0 installs were displayed.
Change Show to 1000
Click the box to select all items
Choose action, delete
Click yes to confirm deletion
Wait for the page to reload
Go back to step 4 and repeat until the items with 0 installs are gone

5000+ records gone in under 1 min :)