I just aquired an X61 with an X6 Ultrabase. The X6 Ultrabase is P/N 42W4635 and FRU P/N 42W4634. The part number on Lenovo's website appears to be 40Y8116 though, so I'm not sure if it's the same part. Mine does not have an optical drive in it, so I would like to purchase a DVD burner. External is not an option. Will any slim IDE DVD burner work, like these on NewEgg, or do I have to buy one directly from Lenovo?