I have an Asus F8SN-C1 running Windows 7 Ultimate 32-bit SP1 and for a long time actually have run into issues where it hard locks from anywhere from 30 seconds to 3-5 minutes and then will beep once and I can start using it again. Everytime I have had it happened has been with web browsing in Chrome I do believe, have updated graphics driver, no change, java and flash are update and Chrome is updated issue persists.
System isn't overheating have had speedfan running with cpu temp around 45 celcius, and happy to answer any other questions to try and get it answered, prepared to reinstall or....possibly upgrade to windows 8 though I think that is the last thing I want to do.
More aboutrandom lockup
Also when it occurs, the keyboard seems to stop working first, then mouse will not move what so ever until the system makes a beep
Turn off Chrome's OpenGL engine. It's been known to cause problems. Otherwise a hard lock typically indicates a hardware issue.