you need to run the MSI stability test including in your download of this overclocking tool.
after the test of 2 minutes you must tjek how hot the GPU is. i whold say: dont go too much over 80 C.
when you are happy with the result, try some games and look for anything unusual. like some black spikes. (called heatspikes) those indicate that the GPU is too hot.
also if the OC is unstable it will freese.
dont worry about if it freeses. that is normal when you are going for the max OC. just restart.
just remember not to set the option that MSI afterburner should set those settings at windows startup.
you will be happy to hear that the 460. (just liek the 260 and the 560) is the most overclockable card in there serie. ^^
especaly the 460 because that the 470 and the 480 have heating problems. (the 460 is a bf 104 gpu insted of the crappy bf 100 gpu that the 470 and the 480 has)
thank god you didnt buy an 480. that is one of the most crapy shitty fucked up cards in that price. it realy get hot and uses alot of power.