I had the same problem. I couldnt download MMS Pictures that people sent to me. The easiest way to get rid of the sounds and pictures that came with your phone is to use the Explore option on Active Sync and do it from your computer. Also, did you clear your internet Cache? After only 3 weeks, mine had almost 6 megs of crap.
Open internet explore and select
Menu
9 Tools
3 Options
go Down to Memory and hit select and you can see how much is Memory is used.
Press the clear button, wait a few seconds or a minute and you have gained back some of your memory. Hope this helps