we name everything by its serial number/service tag, and that's exactly how these show up. they are indeed called preconfigured computers in 6.9. i'm not familiar with ds 7.x since i only tried using it for a few months before giving up and reverting to 6.x since 7.1 just wasn't ready for prime time in the time frame we needed it. but that's past history.
anyway, here's the really weird part about this. nobody is manually creating these, nor is anyone importing a CSV. i'm one of two people with access to the console and neither of us is doing that. besides - why would we intentionally import duplicate computers? i've seen the same computer name listed as many as 6 times in the all computers list.
another weird factor is that they aren't always yellow - most times they're just gray/offline. they never show any job history (which makes sense for a preconfigured machine). in cases where it's listed 4+ times in the console, it's often listed 2+ times in the winpe preconfigured computer drop-down list.
right now the only method i've found for "quick" deletion of these machines is to pxe boot a VM on my pc, then click the drop down to show the first three, then open the ds console in another window on the host pc, delete those 3, scroll in winpe, delete the next 3, etc etc etc. not fun.