I want to get my AppleTv but all my movies are in rmvb and I need to know if I can play them or not, if I can't play this kind of movies can somebody tell me how I can resolve it.
RMVB files are Real Media files, therefore you need the Real Player, which is free from Real Networks.
In order to play those files on the Apple TV you need to convert them to an Apple TV compliant format.
H.264 and protected H.264 (from iTunes Store): Up to 5 Mbps, Progressive Main Profile (CAVLC) with AAC-LC audio up to 160 Kbps (maximum resolution: 1280 by 720 pixels at 24 fps, 960 by 540 pixels at 30 fps) in .m4v, .mp4, and .mov file formats
iTunes Store purchased video: 320 by 240 pixels, 640 by 480 pixels, 720 by 480 pixels (anamorphic), or high-definition 720p
MPEG-4: Up to 3 Mbps, Simple Profile with AAC-LC audio up to 160 Kbps (maximum resolution: 720 by 432 pixels at 30 fps) in .m4v, .mp4, and .mov file formats
directly from http://www.apple.com/appletv/specs.html