Warhammer 40k D&D 3.x

[mustaju]

This topic has probably been appearing every second month or so, but as someone who rarely finds time to talk to the awesome folks here in GITPF, I really don't have the time to skim through these threads to find what I'm looking for. Maybe some nice folks will point me in a good direction.
So, my old campaign finished two months ago, and since then, everyone has been longing for D&D, but as usual, no-one wants to be the DM. As for some reason people seem to think I'm adept at 40k, I've been asked whether I'd be willing to DM a few sessions of a 40k world. Obviously, this offer did not include any system that would be reasonable to represent 40k, only that it shouldn't be too reminiscent of 4E.
And NO, i do not want to debate whether 3.x or 4E is better, it's the preference of my players.
So, to cut the c**p:
Could you recommend a good, pre-made system for representing Warhammer 40K? Points for being downloadable, free, without nasty spyware and 3.5-like.
Even pointing at threads would help. Thank you so much.
In addition, experiences regarding such sessions are most welcome.
Nota Bene! All people who claim I did something wrong, that I should search the forums more thoroughly or that I'm an unlikable person to begin with: You are correct. And I'm lazy as well.
Thank you in advance!

[SurlySeraph]

Ask and ye shall receive.

[mustaju]

Thanks. This looks awesome. Just for comparison and Pete's sakes, are there any alternative rulebooks or awesome homebrews I should be aware of?

[Stupendous_Man]

huh, interesting.... didn't know that existed!

[RPGuru1331]

Thanks. This looks awesome. Just for comparison and Pete's sakes, are there any alternative rulebooks or awesome homebrews I should be aware of?

Dark Heresy, the actual 40k RPG.