I'm now pretty sure that the hard drive I was booting from (both on the old computer and now) is the actual issue.** Which means I'm going to have to restore from a backup onto the new machine's hard drive which, from past experience, takes awhile (especially since I need to get it to stay on long enough to make sure my backup is up to date).
I can not express to you how much I did not want to do this. I was so happy when booting from the external worked.
Anyway, I will try to get that done this week, though it might not be until Saturday.
Thanks for your patience guys (and thanks again to my friend who got me the new machine in the fist place.)
**Just a reminder that the old machine had a dead hard drive in it and fan troubles so I couldn't have kept using that even if I wanted to. Heh.