Alright here are the settings to reach 4.0 Ghz with a Core i7 920. This will allow you to get 4.0 Ghz on all cores and 4.2 Ghz in turbo mode. This will really help your Super PI Scores. Note: Try my CPU voltage first. If it still blue screens that is a sign that you need more voltage. If it does'nt blue screen then you can try to back it off a little at a time. Do this in .05 increments. For Example 1.43 then 1.38 then 1.33. The same goes when increasing your Vcore Voltage. Print this post out and follow the settings EXACTLY!
Just tried your settings tonight and I have mine now clocked @ 4Ghz, OCCT, Prime stable etc. 1.43v vcore. This is with HT off.

With HT on, it blue screens within 10 minutes of testing every time, I've been up to 1.48v vcore.

Blue screen message is always the same - "A clock interrupt was not received on a secondary processor within an allocated time"
Error 0x101

Other than that, its OK, but I wish I had the eight threads instead of four