|I tried the first Nvidia driver for this model GT520 without change of the issue (from Nvidia site).|
On a temporary HDD :
1- a new installation with windows SEVEN worked a little bit better : no crash, no visible freeze, but one core (CPU dual Core E4500) still loaded permanently around 80 - 90 %, for a overall load of the processor about 40 %, without any application open.
The only issue seemed to be the sound not really fluid. And ACER doesn't provide drivers for this PC for seven.
I didn't test with a heavy application, like games.
However I could burn a DVD with no increase of the overall CPU load.
2- A new installation of Vista gave the same issue (freeze and crash in 5-10 min)
3- I tried with a live Linux (Kororaa, from fedora) and in this case the Nvidia driver worked fine.
It seems to be a windows/driver conflict with this combination of hardware : motherboard ACER F672CR / video Geforce GT520 (or GT440).
I saw on internet a solution with a video card ATI HD5450. Will go back to the store to try an ATI card.