How to add standalone laptops/PC's?

I want a little feedback from both current users of Service Desk and support. We have dozens of laptops through out the company which do no connect to the company network i.e. are standalone used for workshop applications. We want to be able to add them as assets to Service Desk. How would/do other people deal with adding these laptops to Service Desk? Do you add the laptop to the network temporary and let SD+ do the scan? Or do you create extra asset fields such as memory, CPU, etc... and add it as an IT asset? How would the asset be dealt with if it was then used on the network in the future?

Our current asset register is an Access database, I want to import these details into Service Desk. I have created a csv file of the details of the laptops from the Access database, but when I come to import these as a workstation, there is a very limited detail that can be pulled in from the csv file. No option to import the likes of memory, CPU etc... Therefore it is pointing me towards the second option of creating extra asset fields.

Any input would be greatly appreciated