PPCGeeks - I don't get it!!!

I just purchased a Samsung SPH-i325 Ace. I am having problems downloading software from websites that I have used in the past for other phones. Sites like zedge and myxer, as well as this site. Every file (aside from wallpaper) that I try to download, I am told "Error: File cannot be viewed on this device." Is there some setting I need to change or something? I have used all of these sites before with my Motorola Q9c and had no issues, and it's a Windows-based device just like the Ace. They are eerily similar in fact. Can anyone help me? I'd love to get sMMS on this phone as well as use my other sites for ringtones. I'd appreciate any info!!!

Thanks