Oooo, too bad. What type of paste was that? I'm only using Noctua because it requires such a small amount, and is non-conductive.
I start with a small ball of it right in the middle, and with a latex gloved finger circle it out to the perimeter in non-stop motion. The ball is about 3.5 mm in diameter, and a good way to put it is that the amount is enough that you just can't see through it, but close. This is done before placing the processor....
On your other post you got some advice. Step back a bit.... check the boot block date in your BIOS. What processors you can use are quite different if you have the old boot block date versus the newer one. That is all in here.
For the Z600 going up to 130W processors is quite expensive..... they need a rare and expensive heatsink/fan. One socket can use your Z400 original, but the other will be hard to find. I've posted all about that here.
Good luck.... get a tiny pick, a good light and take your time. You might end up with a Z600 running on 1 processor only, in socket 0. Check your boot block date, and then get the fastest 95W hexacore approved by HP for your version if that ends up being the case.