If you still own them they would remain on the balance sheet. They effectively have a zero value even if you retain the acquisition value as the asset value and post all accumulated depreciation in a single account (I do).
Disposed of is different. How disposed? Put out with trash? Put them on a Sales Receipt at zero sales price. Taken to recycle for $100/ton? Sell them for salvage cost and recover the depreciation taken as ordinary income (or just claim the cash as income, still selling them at zero)
Final step is making them "inactive"
