I have an Acer Aspire 5670 with a Matshita CD/DVD writer drive. I upgraded Windows/XP with SP3 and discovered that the drive had disappeared just like you. The fix removing the Registry entries did make my drive return and was usable by all of my other programs, but not with Roxio Easy CD/DVD Creator Version 7.5. I had the same problem with not finding Easy CD/DVD Creator in ad/remove programs. I tried to reinstall Version 7.5 but was prevented from doing so because the install program reported that the version it was replacing had newer modules. I ended up forcing a new installation of Version 7.5. Still no CD/DVD drive and when I rebooted, Windows didn't see the drive either. I ran Easy CD/DVD Creator Repair which ended in the same result.
I have no solution to this except to toss Easy CD/DVD Creator out the window and use other programs. I wasted 4 hours on this.
I stumbled on one of these messages (can't find it now) that gave me the solution to all of this. Roxio has developed an engine update that fixes the problem. You first remove the filters in the Registry (referenced above), then install the engine update. The update says it applies to Version 7 adn above, but others found that it also applied to older versions. The update is the file pxengine4_10_28a.exe. If you can easily find it on the Roxio site you are a better person than I! The Search function on this site leaves a lot to be desired.
Anyway, the update fixes the SP3 disk disappearance problem.