I did a quick search on my system (I have a Moviebox 700-USB, not a Dazzle) - some places I found Dazzle-related files. Heed the usual "health warning" before manually diving in and changing/removing stuff in the innards of Windows [;-)]:
C:\Program Files (x86)\Common Files\Pinnacle\Driver\Video - several sub-folders of drivers, although I think those folders were put there by the installation of a legacy version of Studio, not a recent one (19 or later)
C:\Windows\System32\INF - there may be .INF or .PNF files starting with "oem" - you would need to look inside the .INF files with a text editor, if you find one related to the Dazzle, remove both it and any companion .PNF file sharing the same name
C:\Windows\System32\drivers - you may find left-over driver files in here (this is a list of possible files I found in the one of the driver INF files - I don't have any of these installed as I don't have a Dazzle device):
emProp.ax
emProp64.ax
emVFW.dll
emYUV.dll
emUSD64.dll
emScan64.sys
emFilter64.sys
emDevice64.sys
emTwain.ds
C:\Windows\System32\DriverStore\FileRepository - may contain folders with Windows' reference copies of installed Dazzle drivers - the folder names aren't nice but you may spot text such as "DVC100" in the names
There could be other stuff...
An alternative to manually removing stuff would be to use the Revo Uninstaller tool (the free version would likely be "powerful enough") - from inside Revo launch the Dazzle driver uninstaller and then let Revo scan for and identify what it thinks are stray files or settings left behind (you can then review them and choose whether to delete or keep)
HTH
Richard