Extremely loud Xbox 360

I was trying to fix my E74 error by opening up my 360 (again...) after watching a video here on YouTube and following what the guy was doing. Basically re-applying thermal paste (Arctic Silver 5) to the GPU. So after applying the paste and re-attaching the heatsink, I turned it on without the fans connected just so it can 'cook' and settle in. Then I plugged in the fans and they went to, what appears to be, full speed.

As you can tell, they're pretty loud!

P.S. I won't stop there. I'm gonna try and fix this. I only had nail varnish remover (not my own BTW!) to clean off Microsoft's paste and it didn't work that well. There was still some left when I applied my Arctic Silver 5. So when I get paid I'm going to get some paste remover and re-attempt fixing my 360.