QB Issue Resolution:

If you have the used computer as inventory with cost, and you add the components with cost then yes you  are  doubling cost.

Create the items, zero cost, zero qty

use inventory adjust, set the adjusting account to the cash bank account, and lower the computer item

Check the cash account regster to fimd the value of the adjustment, that is the total amount for all the part items.

Then create and use a dummy vendor to buy the parts from.  You will have to guesstimate the cost of each as long as the sum, total does not exceed the adjustment value you are fine.

Resolution for Issue 'Product Transformation on Inventory' available: Yes (Solved).
Source: Intuit Community forum.

Product Transformation on Inventory: this issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the issue yourself by looking for a resolution described below. If it is a complex issue or you are unable to solve the issue, you may contact us by clicking here or by using other support options.

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