I don't really understand how a CPU can be sold "for parts" as it's not like you can realistically take it apart, test and replace the damaged components.
If you bought it on eBay, I know that the term would have been "not working/for parts only".
Unfortunately, it seems that you took a gamble and lost.
Sounds like you paid for a learning experience. If you bent the pound back, got it to fit in the socket, and it doesn't work then there's not really anything else to do. This is assuming your MB actually supports the CPU.
If you've straightened the pins, I'm out of ideas. I'd just be glad it didn't zap my motherboard somehow.
fixing pins is not easy (as you may well know). Installing the CPU wrong AND powering it up in that way seems almost impossible, so unless you know for sure that's what happened, I would still put my money on: "getting the pins back to perfection should make it post" maybe one of the pins that you bent back has a bad contact point with the cpu and needs to be repinned. I check out Northrigde repair videoblog sometimes, and repinning looks really, pretty hardcore so, suit up if you're going this route.
Also, to get some perspective:
Did any one of us here ever kill a CPU? I mean bent pins can happen to any nervous hardware installer, but maybe by pushing it beyond it's limits with overclocking? I have had a bit of fun with CPU's but none of them died on me.