2500K IGP Overclocking

The IGPs are generally very sensitive to overclocking and even then you won't get much performance out of it

Hmmm so nothing at all?

even if you could (and I don't think you can), it wouldn't be worth it. The IGPs are good enough for really old games that don't require it to be overclocked but that's it. It's not going to take anything from unplayable to playable

You didn't say which board you have (or are going to have) but the BIOS in my Asus P8Z68-V LE DOES have a setting to increase the max frequency of the iGPU with GPU Boost. The name "GPU Boost" is specific to Asus though, I think, but I'm guessing that another brand or two might allow that too, I just can't tell you that for sure.

I have a Biostar TZ77B. I don't want to try to game or anything. That can wait for my discrete graphics card. I just want to be able to run Windows and watch HD videoes smoothly for now. Would the IGP be able to do that on it's own?

Yeah, HD 3000 is more than sufficient for that, even without OC'ing.

Enough for 1920x1080?

Yep, that's what it's meant for actually. Not gaming worthy, but plenty for 1080p HD video.