CPU sudden temperature increase

I would check what active services are running. It might be that with the installation of SP1, something is running in the background which is causing the temps to increase. Though you PC may be in idle state, there can be services in the background using up processes & generating heat.

10 degrees?!
there is something else going on here. But lets make sure;
-are you comparing computer temps from very different ambient room temps.
-have you done anything else to the computer?
-open task manager and see what is eating CPU time.
-where are you getting these temps from? Download HWMonitor and see what is says for TMPIN2.

I forgot to add that when I run Ubuntu my CPU temp is running normal. So this does mean that it is software. Thats why I think its SP1, I could be wrong but thats my guess. I also get my CPU temp from my motherboard. Once I can get to my computer I can check what programs are running.

Top 3 programs while idle:
Explorer.exe (31k)
dwm.exe (20k)
CCC.exe (20k)

The rest are under 5k

What kind of cpu cooler are you using? Are all your case fans running? Also winter is over so your room temp may be a factor. I havent installed Win7 SP1 yet so it could be extra services installed with SP1

Maybe you can disable dwm.exe and see what happens. Here is some info. on it: http://www.trickyways.com/2010/03/what-is-dwm-exe-compl...

Exactly the same issue here with an Asus Sabertooth X58, i920 @ 3.6Ghz. I monitor my CPU temp closely during overclocks and it has easily jumped 5 degrees at idle, since the installation of Win7 (I've JUST finished installing it and without a doubt it was SP1, or something related to SP1 during install) I am using a Corsair H50 cooling system.

Update, I recently did a fresh install of Win7 Ultimate. The temp on idle is what It should be 25-30c. I'll test what the CPU temp is after I install SP1, but this does show that this problem is a software related issue.