I looked to that post to personalise ringtones. But ringtones are not available as 'Alerts'.
Do you think there's any way to do it?
You can not provide personalize alert sounds without rooting your phone. I don't have it on me (I will try to find it tonight when I am home), but I believe I have seen an app on the XDA forums that allows you to replace existing alerts with new ones.
Again, your phone has to be developer unlocked and have the root tools supplied. If anyone knows of the app I am referring to, please edit this to provide the name.