The Video Toaster 2000 will run on VT4000 software. When you install Vt4000 sw v4.1 from CD, it will ask you which VT you have, just choose VT2000.
I got running VT4000 on A2000 with 4.1 sw and VT2000 on A2000 with v4.1.
To do blue/green Chromakey, you need separate chroma device, like "Chromkey plus", if you dont have one you can only use Lumakey on Black or White background on VT.
You can install SCSI CDROM on A2000HD, just use longer SCSI cable. CDs are available on EBAY last time I checked.
Good luck.
Isn't there more to installing a CD drive to an A2000 than just adding it to the SCSI chain?
