After trawling through reams of forum info it appeared that the only solution was to use the 430 designjet plotter driver which worked but only in black and white / greyscale. However, I did eventually find a solution thanks to user jdm13 on the HP forums.
Update 7/5/13 from user Jeff Anderson
I had the driver but, thought it was buggy because I kept getting a corruption error when I tried to install it in windows 8. But, I learned that I just needed to temporarily turn off Integrity checks and it loaded fine.
I bought a laptop with windows 7 64 bit, connected to the plotter HP 450C A / 0 with usb adapter, installed the drivers I downloaded from this post, I select my model (HP 450C) and I try to print but nothing is printed.
What did I do wrong, may be the parallel cable / usb wrong?
thanks
Conexant's MicTray64.exe is installed with the Conexant audio driver package and registered as a Microsoft Scheduled Task to run after each user login. The program monitors all keystrokes made by the user to capture and react to functions such as microphone mute/unmute keys/hotkeys. Monitoring of keystrokes is added by implementing a low-level keyboard input hook [1] function that is installed by calling SetwindowsHookEx().