If you go into Start - run
it is called IMAPI CD Burning COM Service
Using Nero along side Roxio should cause no problems. If unsure set the service to manual.
Just right click on it and go into properties.
If worried make a restore point, then install Roxio. If it doesn't work, just un-install or restore the machine to an earlier date.
If you are having trouble playing actual video cd's. Put the cd into the machine explore the cd.
Go into the MPEGAV Directory, and use a third party dvd player like Power DVD XP for Win XP to play back the example.DAT file.
Just right click the file and open with "powerDVD"
You can get it for about £10 or less nowadays.
Also check you have the latest drivers for your graphics card. Because the actual playback of a video cd should not be effected by what burning software you have installed.
:-) hope it helps