I just got a used dv.NOW AV. It worked on the other system, but on two of mine, when I install it and hit the power, the PC won't even POST. Both boards are VIA chipsets with Athlon XP CPUs.
I used to work for Dazzle-FAST before our parent company decided to sell us away. It's refreshing to see users who still use the DV.now AV.
Unfortunately, however, the DV.now AV was designed to enumerate under INTEL conditions (some AMD's will work), but most don't. If you machine won't post, you most likely have an incompatible chipset. You may consider changing the PCI slot location (if DV.now AV is being shared on the same IRQ as the video card), but most likely, you will run into the same problems. If you move it over to an INTEL, you should be fine.
I've had no problem with DV.now AV on AMD systems; both single and dual processor XP/MPs. Currently running it on a ASUS A7M-266D motherboard with Win2K. However, in the early days (before Dazzle/SCM bought the line from FAST Multimedia) there were issues with some VIA chip-based motherboards. The DV.now AV forum posts from several years ago address this and might prove of interest if changing slots does not solve the problem.
A separate issue is use with Windows XP Pro. A lot of folks (including me) have not had success trying it.