how can I check whether Intel's AVX is enabled on my computer?
To enable or disable AVX instructions you can use this commands:
bcdedit /set xsavedisable 0
bcdedit /set xsavedisable 1
Open your command prompt and type it, then hit the enter button.
According to Microsoft this will only be supported under Windows 7 Service Pack 1 (slightly offtopic but factual) which is due out this month. I can't find any detail as to enabling/disabling it - I assume it'll be on by default and your code needs to be written to use it. Maybe somebody else will have some insight on this?