I had the same problem with Error 1714 on several PCs and the above suggested procedures (MSI Clean, ect.) didn't work! Unfortunately NI-IMAQ Versions 2.51, 2.55 and 2.6 produced the same installer error. Until NI adresses this problem (e.g. provide information about the exact registry key, that causes this error) try this:
Workaround 1) If you have a PC without NI Software, install NI-IMAQ first, reboot, make sure your board(s) appears in MAX, then install LabVIEW, then run the NI-IMAQ installer again to add the NI-IMAQ VIs.
Workaround 2) On a PC with NI Software (specifically LabVIEW 6.02 seems to be problematic), deinstall LabVIEW, reboot, install NI-IMAQ, reboot, make sure your board(s) appears in MAX, then install LabVIEW, then run the NI-IMAQ
installer again to add the NI-IMAQ VIs.
Hope this helps!
Best regards, Robert
PS: Both workarounds have worked for me on different Windows 2000 machines.