Nec 3500 Problems

Hi Everyone,
Im Getting Desperate For Help Now. Im Quite New To Computers And Therefore Would Really Appreciate Some Help From Someone Who Knows. I Have A Pentium 4 2.4ghz Processor And An Nec Dvdrw 3500ag. The Problem Comes When I Am Backing Up My Dvd Collection. I Am Using Dvd Shrink 3.2 To Put The Movie Onto My Hard Drive Which Is Fine. I Am Also Using Nero 6 Toburn Off The Movie Onto An 8 Speed Disc.the Discs Are Anv Single Layer 8 Speed With A Ritek Dye. When First Installed It Burnt At 8 Speed Then The Next Time I Booted Up It Was Taking 24 Minutes To Burn A 4 Gig Disc And Only Verifying At 2 Speed As Opposed To 14 Speed As It Had Been. I Then Went On Necs Website And Downloaded A Driver Which Flashed The Driver Or Something And It Worked Again At Full Speed. Yet Again Though When I Rebooted The Pc It Slowed Down To 24 Mins A Burn 45 Mins If You Include The Verifying. Does Anybody Know What The Problem Is. I Would Appreciate Any Help You May Give As Its Beginning To Really Bug Me Now.
Yours Hopefully