Hello Khan, 

I'd be happy to help you with this.

Let's pull up the QuickReport for this inventory item to double-check if there are no transactions using it.

Here's how:

1. From the Lists menu, choose Item List.
2. Right click on the inventory item, and choose QuickReport: [Item Name].
3. Choose All from the Dates drop down option, and click Refresh.
4. If there are transactions on the report, just double click it, and press Ctrl+D on your keyboard.
5. Click OK to confirm.

Then try deleting the inventory item again. If you can't find any transactions, your best bet is to make it inactive.

Let me know how it goes. I'll be waiting to hear back.