which writer came with your dell, check jumper settings on it, as from what i have seen or rather read, they like to have them jumpered as cable select, so if your saying it came with benq1625 and that worked OK then it became faulty and you simply then bought another 1625 and you set that as master and it would not recognize disc's and now you got lg and your having trouble with that, i am wondering if you should jumper the 2nd 1625 as cable select and the lg the same, in case the way dell have your bios tied to cable select for correct functioning, i hate cutdown bios shopfitted crap, i never have this issue as i build my own and never use cable select, apart from my xboxes.