Bad news seems to be everywhere right now, whether it's about Milestone perhaps not getting Froyo and now. If you are big fan of the Aria from AT&T then you probably know that the carrier has crippled the phone so that you cannot download applications from third parties; simply put, from nowhere other than the Android Market. You can see in the picture below that the option is not even present, since AT&T has taken it out completely.
However, here comes the good news. The guys from Android Central have developed a little program for Windows called the "Sideload Wonder Machine", this app will allow you to install any .apk file you wish for to your Aria without rooting your phone. The app is available for download now.