Radeon 5970 prevents the computer from booting from the first time

Thanks ok, let's see.. your temps seems a little bit too high, but those screenshots cant speak for themselves... could you upload Resource Monitor screenshots?

And where are you getting those temps at? which program? i'd suggest using CPU-Z and GPU-Z or Speccy!

CPU: -23ºC? something is NOT right there hehe...

Do those things and report back, please! :)

Sorry, the computer was lagging so when I tried to capture the whole window to make a screenshot, it captured only a small part, instead. I got it from SpeedFan.

Here are other screenshots from Resource Monitor. I took them later, though, when the problem seemed to have gone.