I have a copy Start CS 1650 with the error code C-400 any Ideas

There is no C400 code, but there is a C4000 and its a pretty common code on these boxes. it's pointing to your laser unit. definetly not easy to get to. you will have to have laser unit replaced or sometimes i have had luck pulling out laser, pulling polygon mirror out and lubricating the shaft. that only works about 50-60% of time however and if you are paying a tech to do this work, you may just want to replace it as it is fairly time consuming to get laser out.

hth,
razors