Scroggs,
I'm probably no more qualified than yourself to answer this, but, as they say, two minds better than one..
Presuming its not just coincidence, and that the drive replacement has something to do with it...
Have you checked the security of all the plugs / sockets
to and from the motherboard and all drives (annd re-checking the PSU connections in particular?
Have you another CD drive you can try.. perhaps the drive detection during boot is picking up a problem. Does the old drive allow boot to complete.
Was this an additional drive. If so, are the master / slave jumpers configured correctly?
I dont suppose (I don't see why you should have) you disconnected the HDD IDE plugs and got them 'mixed up'?
Hope this helps.
Tim