when doing something like this... changiing that much hardware, this is a HUGE shock to the system, your best bet is to reinstall windowns ontop of the old install, backup all files and then reformat and start all over again.
Sometimes you can get away with it, but you are better off in the long run to reformat, if you do ever get the PC to boot properly, you will notice that your computer will more then likely be running at half of its performance.
if you have another PC, put that HD in it, get all your data from it that you want/need and then reformat.... will save you a huge headache in the end.... probably not what you want to hear, but it is your best option.
Also when doing this , you might want to reset your BIOS and let it detect all of it manually, its usulally pretty good at doing this...
hope this helps...