I got a ND5500a.  The burn times come in around 20-21 minutes which seems a little slow 4x.  So far I have tried a 8x Ritek, 4x Memorex and a 4x RicohJP +RW all with the same results.  I tried to update IDE driver, DMA is on and not getting any errors in Nero.  Running XP Pro Service pack 2.  Same results in 2k.  Anyone have any experience with this drive?  Any assistance greatly appreciated.